Failure to resurface the patella during total knee arthroplasty may result in more knee pain and secondary surgery

Patellar denervation with electrocautery in total knee arthroplasty without patellar resurfacing: a meta-analysis

PURPOSE

The impact of patellar denervation with electrocautery in total knee arthroplasty (TKA) on post-operative outcomes has been under debate. This study aims to conduct a meta-analysis and systematic review to compare the benefits and risks of circumpatellar electrocautery with those of non-electrocautery in primary TKAs.

METHODS

Comparative and randomized clinical studies were identified by conducting an electronic search of articles dated up to September 2012 in PubMed, EMBASE, Scopus, and the Cochrane databases. Six studies that focus on a total of 849 knees were analysed. A random-effects model was conducted using the inverse-variance method for continuous variables and the Mantel-Haenszel method for dichotomous variables.

RESULTS

There was no significant difference in the incidence of anterior knee pain between the electrocautery and non-electrocautery groups. In term of patellar score and Knee Society Score, circumpatellar electrocautery improved clinical outcomes compared with non-electrocautery in TKAs. The statistical differences were in favour of the electrocautery group but have minimal clinical significance. In addition, the overall complications indicate no statistical significance between the two groups.

CONCLUSIONS

This study shows no strong evidence either for or against electrocautery compared with non-electrocautery in TKAs.

LEVEL OF EVIDENCE

Therapeutic study (systematic review and meta-analysis), Level III.

A randomised, controlled trial of circumpatellar electrocautery in total knee replacement without patellar resurfacing: a concise follow-up at a mean of 3.7 years

In the absence of patellar resurfacing, we have previously shown that the use of electrocautery around the margin of the patella improved the one-year clinical outcome of total knee replacement (TKR). In this prospective randomised study we compared the mean 3.7 year (1.1 to 4.2) clinical outcomes of 300 TKRs performed with and without electrocautery of the patellar rim: this is an update of a previous report. The overall prevalence of anterior knee pain was 32% (95% confidence intervals [CI] 26 to 39), and 26% (95% CI 18 to 35) in the intervention group compared with 38% (95% CI 29 to 48) in the control group (chi-squared test; p = 0.06). The overall prevalence of anterior knee pain remained unchanged between the one-year and 3.7 year follow-up (chi-squared test; p = 0.12). The mean total Western Ontario McMasters Universities Osteoarthritis Indices and the American Knee Society knee and function scores at 3.7 years' follow-up were similar in the intervention and control groups (repeated measures analysis of variance p = 0.43, p = 0.09 and p = 0.59, respectively). There were no complications. A total of ten patients (intervention group three, control group seven) required secondary patellar resurfacing after the first year. Our study suggests that the improved clinical outcome with electrocautery denervation compared with no electrocautery is not maintained at a mean of 3.7 years' follow-up.

The patella in total knee arthroplasty: to resurface or not is the question

The decision to resurface the patella during total knee arthroplasty remains controversial. Even though some surgeons routinely resurface the patella to avoid the increased rates of postoperative anterior knee pain and reoperation for secondary resurfacing, others selectively resurface based on the presence of anterior knee pain, notably damaged articular cartilage, inflammatory arthritis, isolated patellofemoral arthritis, and patellar subluxation and maltracking. The anatomy and biomechanics of the patellofemoral joint, combined with advances in surgical technique and prostheses must be taken into account when making a decision to resurface the patella. Accurate component implantation is imperative for a successful outcome if the patella is resurfaced.

Non-anatomical capsular closure of a standard parapatellar knee arthrotomy leads to patellar maltracking and decreased range of motion: a cadaver study

PURPOSE

A parapatellar approach disrupts the medial soft tissue stabilizers of the patella. We hypothesized that soft tissue realignment during arthrotomy closure of native cadaveric knees influences patellar kinematics leading to decreased range of motion.

METHODS

Parapatellar arthrotomy was performed in seven native human cadaveric knees that did not contain arthroplasty components. Capsular closure was performed with figure-of-eight sutures in five different positions for each specimen. The capsule was closed anatomically, and then shifted 1.5 or 3 cm distal, or 1.5 or 3 cm proximal relative to surgical markings of the patellar poles. In each closure position, real-time patellar kinematics and range of motion were recorded using a navigation system with patellar tracking function.

RESULTS

Maximum knee flexion was significantly reduced with closure shifted 3 cm proximal (133° ± 8.2°, p < 0.001) or distal (139° ± 6.4°, p < 0.05) compared to anatomical closure (147° ± 4.1°). All closure positions significantly influenced patellar rotation at 45°, 90°, and 120° of flexion (p < 0.001). Closure 1.5 or 3 cm distal increased lateral patellar shift relative to the mechanical axis (p < 0.01). Patellar tilt was significantly decreased at 90° and 120° by closure 3 cm distal (p < 0.01) and at 120° when closed 1.5 cm distal (p < 0.05).

CONCLUSIONS

Imprecise arthrotomy closure significantly impacted patellar kinematics and passive range of motion. Therefore, every effort should be made to provide anatomical closure of the extensor mechanism to preserve native patellar movement kinematics.

LEVEL OF EVIDENCE

V.

Determinants of anterior knee pain following total knee replacement: a systematic review

PURPOSE

Anterior knee pain (AKP) following total knee replacement (TKR) is both prevalent and clinically relevant. The purpose of this study was to systematically review the peer-reviewed literature, and to identify and assess the different modifiable and non-modifiable determinants that may be associated with the development of AKP in patients following primary TKR.

METHODS

A systematic computerized database search (Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, and Google Scholar) was performed in January 2012. The quality of the studies was assessed using the GRADE approach.

RESULTS

A total of 54 articles met the inclusion criteria. Variables that have been researched with regard to the prevalence of AKP include patient and knee-specific characteristics, prosthetic design, operative technique, treatment of the patella, and time of assessment. A weak correlation with AKP was found for specific retained presurgery gait patterns. A weak recommendation can be given for the use of femoral components with a posterior centre of rotation, resection of Hoffa's fat pad, patellar rim electrocautery, and preventing combined component internal rotation. The correlation between postsurgical AKP and the degree of patellar cartilage wear, tibial component bearing strategies, and patellar resurfacing is inconclusive. Due to substantial heterogeneity of the included studies, no meta-analysis was performed.

CONCLUSIONS

No single variable is likely to explain the differences in the reported rates of AKP, although variables leading to abnormal patellofemoral joint loading appear to be of special significance.

LEVEL OF EVIDENCE

III.

Early PROMs following total knee arthroplasty--functional outcome dependent on patella resurfacing

Patella resurfacing during primary total knee arthroplasty (TKA) remains controversial. Variation in published results for patella resurfacing may potentially be explained by differences in design between TKA brands. We interrogated NJR-PROMs data to ascertain whether there is an early functional benefit to resurfacing the patella, both overall and for each of the five most popular primary knee designs through use of the Oxford Knee Score. A total of 8103 resurfaced TKAs and 15,290 nonresurfaced TKAs were studied. There was a large variation in the proportion of knees undergoing patella resurfacing by brand (Nexgen=16% versus Triathlon=52%). Patellar resurfacing did not significantly influence the magnitude of improvement in overall knee function or anterior knee-specific function irrespective of TKA brand or for cruciate retaining versus sacrificing designs.

Three dimensional CT-based virtual patellar resection in female patients undergoing total knee replacement: a comparison between tendon and subchondral method

Background

Due to its small size, variable shape, and lack of distinct anatomical landmarks, osteoarthritic knees make a precise patellar resection extremely difficult.

Methods

We performed virtual patellar resection with digital software using three dimensional computed tomography scans of knees from 49 patients who underwent primary total knee replacement at our hospital. We compared 2 commonly used resection methods, the tendon method (TM) and the subchondral method, to determine an ideal resection plane with respect to the symmetry and thickness of the patellar remnant.

Results

The TM gave a thicker resected patella, and a less oval cut surface shape, which gives better coverage for a domed prosthesis. Both methods, however, gave a symmetric resection both superior-inferiorly, as well as mediolaterally.

Conclusions

Although TM appears statistically better with respect to the thickness and cut surface shape, only further intraoperative studies with long-term clinical follow-up may provide us with the most appropriate patellar resection method.

LCS mobile bearing total knee arthroplasty without patellar resurfacing. Does the unresurfaced patella affect outcome? Survivorship at a minimum 10-year follow-up

BACKGROUND

Patellar resurfacing during total knee arthroplasty (TKA) remains controversial. The aim of this study was to evaluate the long-term outcomes of a mobile-bearing TKA without patellar resurfacing.

METHODS

We assessed the outcomes in 503 patients (600 knees) who had cemented LCS (low contact stress) mobile bearing TKA without patellar resurfacing at a minimum follow-up of 10 years. Clinical outcome scores and radiological assessment were used.

RESULTS

Four knees were revised, two had bearing dislocation and nine patients (1.5%) had secondary resurfacing for anterior knee pain. There were no radiolucent lines or osteolytic defects on radiographic evaluation. The overall survivorship was 97.8% with re-operation for any reason as the endpoint.

CONCLUSION

Non-resurfacing of the patella does not adversely affect the outcome of the LCS mobile bearing TKA at minimum 10 years follow-up.

A randomized controlled trial comparing patellar retention versus patellar resurfacing in primary total knee arthroplasty: 5-10 year follow-up

Background

The primary purpose of this randomized controlled trial (RCT) was to compare knee-specific outcomes (stiffness, pain, function) between patellar retention and resurfacing up to 10 years after primary total knee arthroplasty (TKA). Secondarily, we compared re-operation rates.

Methods

38 subjects with non-inflammatory arthritis were randomized at primary TKA surgery to receive patellar resurfacing (n = 21; Resurfaced group) or to retain their native patella (n = 17; Non-resurfaced group). Evaluations were performed preoperatively, one, five and 10 years postoperatively by an evaluator who was blinded to group allocation. Self-reported knee-specific stiffness, pain and function, the primary outcomes, were measured by the Western Ontario McMaster Osteoarthritis Index (WOMAC). Revision rate was determined at each evaluation and through hospital record review.

Results

30 (88%) and 23 (72%) of available subjects completed the five and 10-year review respectively. Knee-specific scores continued to improve for both groups over the 10-years, despite diminishing overall health with no significant group differences seen. All revisions occurred within five years of surgery (three Non-resurfaced subjects; one Resurfaced subject) (p = 0.31). Two revisions in the Non-resurfaced group were due to persistent anterior knee pain.

Conclusions

We found no differences in knee-specific results between groups at 5–10 years postoperatively. The Non-resurfaced group had two revisions due to anterior knee pain similar to rates reported in other studies. Knee-specific results provide useful postoperative information and should be used in future studies comparing patellar management strategies.

ClinicalTrials.gov identifier

NCT01500252

The effect of patellar replacement technique on patellofemoral complications and anterior knee pain

Routine patella replacement with total knee arthroplasty has not been universally adopted because of associated patellofemoral complications such as anterior knee pain (AKP). In the proposed technique, the articular surface of the lateral facet of the patella is excised to the depth of the subchondral bone, and the medial facet is then cut parallel to the anterior surface. We evaluated any correlation between various radiographic parameters and AKP in 100 consecutive fixed-bearing posterior-stabilized total knee arthroplasties. There were no cases of fracture, avascular necrosis, subluxation, dislocation, patellar baja, or overstuffing of the patella. Anterior knee pain was present in 11% of cases, and no cases were severe or disabling. There were no correlations between AKP, range of motion, patellar size and shape, and any of the radiographic parameters.

Comparison of patellar retention versus resurfacing in LCS mobile-bearing total knee arthroplasty

PURPOSE

The aim of this retrospective study was to compare clinical outcomes of total knee arthroplasty (TKA) with and without patellar resurfacing using the Low Contact Stress (LCS) mobile-bearing prosthesis in 275 osteoarthritic knees (199 patients) after a minimum of 7 years of follow-up.

METHODS

Patients were divided into a patellar retention group (132 knees) and a resurfacing group (143 knees), with median follow-up durations of 7.8 years (range, 7-8.5 years) and 8.5 years (range, 7-10.6 years), respectively. The demographics of the two groups were otherwise matched. The patelloplasty was performed for patellar retention. Patients were evaluated by a blinded, independent observer using Feller's patellar score, the Knee Society score, patient satisfaction, patellar tilt, and lateral displacement.

RESULTS

Patellar resurfacing was not superior to retention with respect to any of the measured variables. Eight knees (6.1%) without and 6 (4.2%) with patellar resurfacing had anterior knee pain related to the patellofemoral joint (n.s.). The reoperation rate related to the patellofemoral joint was 0.8% (n = 1) in the retention group compared with 2.8% (n = 4) in the resurfacing group (n.s.). In the 35 patients who underwent bilateral TKA with patellar resurfacing on only one side, there were no significant differences between the two sides in subjective preference, clinical scores, or functional ability.

CONCLUSIONS

The clinical and radiographic outcomes of TKA with the LCS mobile-bearing prosthesis showed no significant difference between the two groups after a minimum of 7 years of follow-up. The findings in this study suggest that patellar retention with a patelloplasty may be viable as a routine procedure, even in knees with advanced patellofemoral arthritis, if soft tissue balancing and a patella-friendly prosthetic design are properly used.

LEVEL OF EVIDENCE

Therapeutic, retrospective, comparative study, Level III.

Patellar polyethylene spinout after low-contact stress, high-congruity, mobile-bearing patellofemoral arthroplasty

A low-contact stress, high-congruity, mobile-bearing patellofemoral joint arthroplasty decreases the contact force in the patellofemoral joint, theoretically reducing patellar polyethylene wear and increasing implant longevity. This article describes the case of a 47-year-old obese woman who presented with pain and loss of extension after a low-contact stress, high-congruity, mobile-bearing patellofemoral joint arthroplasty. Radiographs revealed dislocation (ie, spinout) of the patellar polyethylene. Patellar polyethylene spinout is a rare complication of metal-backed, mobile-bearing patellar resurfacing. Theoretically, patellar polyethylene spinout in low-contact stress, high-congruity, mobile-bearing patellofemoral arthroplasty is related to implant design and the placement of the metal base plate. Ultimately, the articulation of low-contact stress, high-congruity, mobile-bearing patellofemoral arthroplasty may be too congruent to resist the forces of the patellofemoral joint, particularly in patients who are obese, and the patellar rotation allowed by this articulation may not be sufficient for all patients. Should patellar spinout occur, replacement of the polyethylene is not sufficient to correct the problem; hence, revision of the patellar and trochlear components is required because it remains unclear whether failure is secondary to patellar or trochlear design deficiencies.

Patellar resurfacing as a second stage procedure for persistent anterior knee pain after primary total knee arthroplasty

PURPOSE

Knee pain after total knee arthroplasty may be caused by an unresurfaced patella. Secondary isolated resurfacing of the previously unresurfaced patella in total knee arthroplasty remains controversial. The aim of this retrospective study was to evaluate the outcome after patellar resurfacing as a second stage procedure.

METHODS

The study included 22 patients (13 female/nine male) who underwent resurfacing of the patella with a mean follow-up of 61.8 ± 39.2 months. The mean age of the patients was 60 ± 9.7 years at the time of operation. The average period between total knee arthroplasty and patellar resurfacing was 26.3 ± 15.2 months. The patient's subjective satisfaction was assessed by a custom-made questionnaire.

RESULTS

The mean Knee Society Score improved significantly from 60.1 ± 8.3 to 77.0 ± 6.3 (p = 0.0063). The mean functional score also improved significantly from 42.7 ± 2.3 to 60.2 ± 3.9 (p = 0.001). Three patients (13.6%) needed further operative revision.

CONCLUSIONS

Although clinical scores showed significant improvement some patients continued to have pain and remained dissatisfied without detecting a specific reason. Further studies are needed to better elucidate the benefit of patellar resurfacing as second stage procedure.

Secondary resurfacing of the patella after primary total knee arthroplasty does the anterior knee pain resolve?

Although it has been shown that the risk of anterior knee pain is greater in patients with nonresurfaced patellae, it is not exactly clear whether the pain would resolve with secondary resurfacing of the patella. Thirty-nine patients (41 knees) underwent secondary patellar resurfacing between January 2001 and January 2007. The mean age was 66 years. The mean body mass index was 29.2 kg/m(2). The average time from primary total knee arthroplasty to resurfacing procedure was 29 months. The mean follow-up was 54 months. Anterior knee pain was the indication for secondary resurfacing in all patients. Although the clinical and functional knee scores improved significantly for whole cohort, 8 patients (8 knees) were dissatisfied with the outcome of surgery. This study highlights that secondary resurfacing is not an always rewarding procedure and patients need to be consulted appropriately with regard to the outcome.

Results of total knee replacement with/without resurfacing of the patella

OBJECTIVE

To study the difference of post-op patellofemoral pain, clunk and crepitus in patients with/without resurfacing at 5 years who had pre-op patellofemoral pain. To study the incidence of post-operative patellofemoral pain, clunk and crepitus following patelloplasty in both the groups.

METHODS

Retrospective review of 765 patients who had total knee replacement with/without resurfacing.Patients were asked about both pre-operative pain and also post-operative pain 5 years after the operation. Patients were examined by a specialist nurse at 5 years post-operatively to check for any patellofemoral clunk/crepitus.

CONCLUSION

In patients with pre-op PF pain, there is significant (p<0.005) higher incidence of post-op clunk in the R group. In patients without pre-op PF pain, there is significantly (p<0.005) higher incidence of post-op crepitus in the R group. In patients with/without pre-op PF pain, the incidence of post-op PF pain, clunk and crepitus is lower than in patients who underwent patelloplasty when compared to the other members of the NR group (statistically significant p<0.005).

LEVEL OF EVIDENCE

Type 4, Case series .

Revision surgery for patellofemoral problems: should we always resurface?

BACKGROUND

Routine patellar resurfacing performed at the time of knee arthroplasty is controversial, with some evidence of utility in both TKA (tricompartmental) and bicompartmental knee arthroplasty. However, whether one approach results in better implant survival remains unclear.

QUESTIONS/PURPOSES

We asked whether (1) routine patellar resurfacing in TKAs resulted in lower cumulative revision rates compared to bicompartmental knee arthroplasties, (2) patella-friendly implants resulted in lower cumulative revision rates than earlier designs, and (3) bicompartmental knee arthroplasties revised to TKAs had higher cumulative revision rates than primary TKAs.

PATIENTS AND METHODS

From a community-based joint registry, we identified 8135 patients treated with 9530 cemented, all-polyethylene patella TKAs and 627 bicompartmental knee arthroplasties without patellar resurfacing. We compared age, gender, year of index procedure, diagnosis, cruciate status, revision, and revision reason.

RESULTS

TKAs had a lower cumulative revision rate for patella-only revision than bicompartmental knee arthroplasties (0.8% versus 4.8%). Adjusting for age, bicompartmental knee arthroplasties were 6.9 times more likely to undergo patellar revision than TKAs. There was no difference in the cumulative revision rate for patella-only revisions between patella-friendly and earlier designs. The cumulative revision rate for any second revision after a patella-only revision was 12.7% for bicompartmental knee arthroplasties while that for primary TKAs was 6.3%.

CONCLUSIONS

Bicompartmental knee arthroplasties had higher revision rates than TKAs. Femoral component design did not influence the cumulative revision rate. Secondary patella resurfacing in a bicompartmental knee arthroplasty carried an increased revision risk compared to resurfacing at the time of index TKA. To reduce the probability of reoperation for patellofemoral problems, our data suggest the patella should be resurfaced at the time of index surgery.

Contemporary femoral designs in total knee arthroplasty: effects on the patello-femoral congruence

PURPOSE

The objective of this study was to evaluate the radiological and clinical correlations between implant design and patellar positioning in patients who underwent TKA utilizing femoral implants with modern designs.

METHODS

Thirty consecutive PFC PS Sigma TKAs, characterized by a new prolonged anterior flange and a "smoother" trochlea, were prospectively reviewed. All patellae were replaced. All patients were evaluated pre-operatively and prospectively at two years follow-up both clinically according to the Knee Society score as well as radiographically. This included computed tomography (CT); patellar tilt, patellar conformity angle, patellar lateralization, and femoral component external-rotation in relation to the clinical trans-epicondylar axis.

RESULTS

Average patellar tilt at follow-up was 3° (±7.5°) with respect to a pre-operative 18.5° (±8.5°). Average patellar congruence angle at follow-up was -3° (range, -11° to +9°) with respect to a pre-operative 10.3° (range, + 1.5° to 25.5°). Average lateralization index at follow-up was 2.7 mm (range, -3.4 mm to +7.1 mm) with respect to a pre-operative 12.2 mm (± 4.8 mm). Femoral component positioning related to the trans-epicondylar axis showed an external rotation of 2.80° (± 2.10°) at follow-up with respect to 5.7° (± 1.80°). Clinically, two (6.6%) patients reported patello-femoral complications related to imperfections in the surgical technique more than the implant's design.

CONCLUSIONS

This study highlighted that modern femoral designs in TKA allow for a correct reproducibility of a normal patello-femoral conformity. Strict surgical principles are paramount to avoid patello-femoral complications even when modern implants are used.

Patellar resurfacing in total knee arthroplasty for osteoarthritis: a meta-analysis

PURPOSE

Whether to resurface the patella during a primary total knee arthroplasty remains a controversial issue. The aim of this study was to determine the advantages and disadvantages of patellar resurfacing during total knee arthroplasty for osteoarthritis through an evaluation of the current literature.

METHODS

A meta-analysis of randomized controlled trials comparing patellar resurfacing with nonresurfacing during total knee arthroplasties was performed. The focus of this analysis was on outcomes of reoperation, anterior knee pain and knee scores.

RESULTS

Ten trials assessing 1,003 knees were eligible. The absolute risk of reoperation was reduced by 4% (95% confidence interval, 1-7%) in the patellar resurfacing arm (between-study heterogeneity, P = 0.06, I (2) = 45%), implying that one would have to resurface 25 patellae (95% confidence interval, 14-100 patellae) in order to prevent one reoperation. Only seven trials provided adequate data of anterior knee pain for a quantitative synthesis. On the basis of those seven trials, there was no difference between the two groups in terms of anterior knee pain. Anterior knee pain after total knee arthroplasty could have multiple etiologies such as surgical factors and nonresurfaced patella is not the sole cause of this problem.

CONCLUSION

The available evidence indicates that patellar resurfacing reduce the risk of reoperation after total knee arthroplasty for osteoarthritis. Not resurfacing the patella might be considered a reasonable option, but patients must accept the increased risk of reoperation for which the quantitative evidence-based synthesis is mild. Based on the evidence provided by this study and those previously published ones, the authors do not now resurface the patella as a matter of routine for patients having a primary total knee arthroplasty for osteoarthritis.

Secondary patellar resurfacing in the treatment of patellofemoral pain after total knee arthroplasty

PURPOSE

This paper reports a prospective review of patients who, between 2004 and 2007, underwent secondary patellar resurfacing (SPR) due to anterior knee pain after a primary total knee arthroplasty (TKA). The aim was to evaluate the clinical outcomes obtained with the SPR and to compare them with radiological findings.

METHODS

A total of twenty-seven consecutive patients met the inclusion criteria. There were twenty-three (85%) women and four (15%) men with a median age of 70 years. The patients were evaluated before and after the surgery with the same functional scores and radiological parameters. Bone scintigraphy was also used in the assessment, and a CT-scan was performed in order to evaluate the femoral component rotation. The median time between TKA and SPR was 18 months.

RESULTS

With a median follow-up of 23 months, seventeen patients (63%) reported a clear subjective improvement after SPR, and patellofemoral scores (primary outcome measure), KSS and WOMAC (secondary outcome measures) showed a statistically significant improvement following the procedure. There were no significant changes after SPR in the Insall-Salvati ratio, the lateral patellar displacement or the lateral patellar tilt. The mean time between TKA and SPR had no statistically significant effect on outcome. The bone scintigraphy revealed increased patellar uptake in seven cases, but this was not related to subsequent improvement after SPR. Rotational computed tomography showed a median internal rotation of the femoral component of 1º. The complications observed were a patellar component loosening and an acute post-infection.

CONCLUSION

No clinical or radiological parameter was found to be related to the final outcome after SPR. There was a discrepancy between functional scale scores and the patient's subjective satisfaction.

Multi-factorial analysis of time efficiency in total knee arthroplasty

The objective of this retrospective review was to determine whether time efficiency could be gained by optimizing the navigation protocol based on a surgeon's specific technique and work flow. Three groups of 30 consecutive patients operated on by the same surgeon were studied. The groups were from three distinct periods between 2002 and 2008. The first group consisted of patients in which no navigation was performed (the control group); the second group consisted of patients in which navigation was performed using a standard protocol; and the third group consisted of patients in which navigation was performed using a customized protocol that eliminated certain steps. Statistical analysis considered analysis of variance for covariates of total time in the operating room, duration of the procedure, and tourniquet time. Chi-square analysis considered categorical variables of age, gender, body mass index (BMI), Knee Society score, and patellar resurfacing against the surgical group. Multiple linear regression analysis evaluated surgical time adjusted for preoperative deformity, BMI, and patellar resurfacing. In the adjusted model, the customized navigation protocol significantly reduced the surgical time by 10 minutes compared to the non-customized navigation. Not resurfacing the patella significantly reduced the surgical time by 9 minutes. Variables of age, gender, BMI, preoperative deformity and Knee Society score were not related to differences in operating time. Time efficiency may be gained with the use of improved computer navigation protocols and patellar non-resurfacing.

Failure of total knee arthroplasty with or without patella resurfacing

BACKGROUND AND PURPOSE

Patella resurfacing during primary total knee arthroplasty (TKA) is disputed and new prosthesis designs have been introduced without documentation of their survival. We assessed the impact on prosthesis survival of patella resurfacing and of prosthesis brand, based on data from the Norwegian Arthroplasty Register.

PATIENTS AND METHODS

5 prosthesis brands in common use with and without patella resurfacing from 1994 through 2009 were included n = 11,887. The median follow-up times were 9 years for patella-resurfaced implants and 7 years for implants without patella resurfacing. For comparison of prosthesis brands, also brands in common use with only one of the two treatment options were included in the study population (n = 25,590). Cox regression analyses were performed with different reasons for revision as endpoints with adjustment for potential confounders.

RESULTS

We observed a reduced overall risk of revision for patella resurfaced (PR) TKAs, but the statistical significance was borderline (RR = 0.84, p = 0.05). At 15 years, 92% of PR and 91% of patella non resurfaced (NR) prostheses were still unrevised. However, PR implants had a lower risk of revision due to pain alone (RR = 0.1, p < 0.001), but a higher risk of revision due to loosening of the tibial component (RR = 1.4, p = 0.03) and due to a defective polyethylene insert (RR = 3.2, p < 0.001). At 10 years, the survival for the reference NR brand AGC Universal was 93%. The NR brands Genesis I, Duracon, and Tricon (RR = 1.4-1.7) performed statistically significantly worse than NR AGC Universal, while the NR prostheses e.motion, Profix, and AGC Anatomic (RR = 0.1-0.7), and the PR prostheses NexGen and AGC Universal (RR = 0.4-0.5) performed statistically significantly better. LCS, NexGen, LCS Complete (all NR), and Tricon, Genesis I, LCS, and Kinemax (all PR) showed no differences in this respect from the reference brand. A lower risk of revision (crude) was found for TKAs performed after 2000 as compared to those performed earlier (RR = 0.8, p = 0.001).

INTERPRETATION

Although revision risk was similar for PR and NR TKAs, we found important differences in reasons for revision. Our results also indicate that survivorship of TKAs has improved.

Is patellar resurfacing superior than nonresurfacing in total knee arthroplasty? A meta-analysis of randomized trials

Conflicting results from abundant studies have made it unclear whether the patella should be resurfaced during total knee replacement. A meta-analysis was undertaken to pool the results of randomized controlled studies (RCTs) and to compare the outcomes and postoperative complications after total knee arthroplasty with patellar resurfacing or nonresurfacing. Sixteen RCTs including 3034 knees between 1966 and December 2009 were analyzed. Reoperation for patellofemoral problems was significantly more likely in the nonresurfacing group (P = 0.03). There was no difference between the two groups in terms of anterior knee pain rate, knee pain score, knee society score and knee function score. The results indicate that patellar resurfacing would reduce the risk of reoperation after total knee replacement, but it seems that the benefits are limited on other aspects, and the analysis of high-quality studies shows no advantage of resurfacing over nonresurfacoing group, even in the aspect of reoperation risk. More carefully and scientifically designed RCTs are beneficial and necessary to further prove the results.

The need for patellar resurfacing in total knee arthroplasty: a literature review

The controversy over whether or not to routinely resurface the patella during a total knee arthroplasty has persisted despite three decades of successful joint replacement procedures. Advocates for routine patellar resurfacing admit the occasional need for secondary patellar resurfacing and declare increased incidence of anterior knee pain in patients with non-resurfaced patellae as a cause for worry. Surgeons that leave the patella unresurfaced cite avoidance of complications that include patellar fracture, avascular necrosis, patellar tendon injury and instability. This review discusses the available literature on patellar resurfacing through an evidence-based analysis of randomized and pseudo-randomized controlled trials and published meta-analyses to date. The published literature seems to favour resurfacing the patellar routinely. Selective patellar resurfacing would be the ideal solution if sound pre-operative criteria could be established. So far, a method for accurately predicting which patients can avoid patellar resurfacing has not been found. Future research looking at patellar resurfacing should concentrate on developing criteria for selecting those patients that would benefit from patellar resurfacing and those that would do as well without resurfacing, and thus, limiting potential surgical complications.

Systematic review of patellar resurfacing in total knee arthroplasty

Controversies existing over resurfacing the patella in total knee arthroplasty remain in the literature. The purpose of this review was to evaluate the effectiveness of resurfacing versus nonresurfacing the patella in total knee arthroplasty. We searched the Cochrane Library, MEDLINE and EMBASE for published randomised clinical trials relevant to patellar resurfacing. The relative risk of reoperation was significantly lower for the patellar resurfacing group than for the nonresurfacing group (relative risk 0.57, 95% confidence interval 0.38-0.84, P =0.004). The overall incidence of postoperative anterior knee pain of the 1,421 knees included was 12.9% in the patellar resurfacing group and 24.1% in the nonresurfacing group. The existing evidence indicates that patellar resurfacing can reduce the risk of reoperation with no improvement in postoperative knee function or patient satisfaction over total knee arthroplasty without patellar resurfacing. Whether it can decrease the incidence of anterior knee pain remains uncertain.

Isolated resurfacing of the previously unresurfaced patella total knee arthroplasty

Postoperative anterior knee pain can be challenging after primary total knee arthroplasty. Isolated patellar resurfacing may provide symptomatic improvement in those patients with an unresurfaced patella. Seventeen isolated patellar resurfacing procedures were performed. Patient outcomes were evaluated using the Knee Society clinical and roentgenographic evaluation systems. Continued symptomatology and overall patient satisfaction were also analyzed. No revisions have been necessary at 47 months of follow-up. Overall, Knee Society knee scores and knee function scores significantly improved. Eight patients (53%) are asymptomatic and were satisfied with the procedure, whereas 7 patients (47%) continue to have anterior knee pain and are unsatisfied. Isolated patellar resurfacing for anterior knee pain in total knee arthroplasty with an unresurfaced patella has a low morbidity and revision rate but may not provide patients with predictable symptomatic improvement.

Does patella resurfacing really matter? Pain and function in 972 patients after primary total knee arthroplasty

BACKGROUND AND PURPOSE

Resurfacing of the patella during primary total knee arthroplasty (TKA) is often recommended based on higher revision rates in non-resurfaced knees. As many of these revisions are insertions of a patella component due to pain, and since only patients with a non-resurfaced patella have the option of secondary resurfacing, we do not really know whether these patients have more pain and poorer function. The main purpose of the present paper was therefore to assess pain and function at least 2 years after surgery for unrevised primary non-resurfaced and resurfaced TKA, and secondary among prosthesis brands.

METHODS

Information needed to calculate subscales from the knee injury and osteoarthritis outcome score (KOOS) was collected in a questionnaire given to 972 osteoarthritis patients with intact primary TKAs that had been reported to the Norwegian Arthroplasty Register. Pain and satisfaction on visual analog scales and improvement in EQ-5D index score DeltaEQ-5D) were also used as outcomes. Outcomes were measured on a scale from 0 to 100 units (worst to best). To estimate differences in mean scores, we used multiple linear regression with adjustment for possible confounders.

RESULTS

We did not observe any differences between resurfacing and non-resurfacing in any outcome, with estimated differences of <or= 1.4 units and p-values of > 0.4. There was, however, a tendency of better results for the NexGen implant as compared to the reference brand AGC for symptoms (difference = 4.9, p = 0.05), pain (VAS) (difference = 8.3, p = 0.004), and satisfaction (VAS) (difference = 7.9, p = 0.02). However, none of these differences reached the stated level of minimal perceptible clinical difference.

INTERPRETATION

Resurfacing of the patella has no clinical effect on pain and function after TKA. Differences between the brands investigated were small and they were assumed to be of minor importance.

Early outcomes of patella resurfacing in total knee arthroplasty

BACKGROUND

Patella resurfacing in total knee arthroplasty is a contentious issue. The literature suggests that resurfacing of the patella is based on surgeon preference, and little is known about the role and timing of resurfacing and how this affects outcomes.

METHODS

We analyzed 134,799 total knee arthroplasties using data from the Australian Orthopaedic Association National Joint Replacement Registry. Hazards ratios (HRs) were used to compare rates of early revision between patella resurfacing at the primary procedure (the resurfacing group, R) and primary arthroplasty without resurfacing (no-resurfacing group, NR). We also analyzed the outcomes of NR that were revised for isolated patella addition.

RESULTS

At 5 years, the R group showed a lower revision rate than the NR group: cumulative per cent revision (CPR) 3.1% and 4.0%, respectively (HR = 0.75, p < 0.001). Revisions for patellofemoral pain were more common in the NR group (17%) than in the R group (1%), and "patella only" revisions were more common in the NR group (29%) than in the R group (6%). Non-resurfaced knees revised for isolated patella addition had a higher revision rate than patella resurfacing at the primary procedure, with a 4-year CPR of 15% and 2.8%, respectively (HR = 4.1, p < 0.001).

INTERPRETATION

Rates of early revision of primary total knees were higher when the patella was not resurfaced, and suggest that surgeons may be inclined to resurface later if there is patellofemoral pain. However, 15% of non-resurfaced knees revised for patella addition are re-revised by 4 years. Our results suggest an early beneficial outcome for patella resurfacing at primary arthroplasty based on revision rates up to 5 years.

Mid-term results with a highly congruous mobile-bearing knee prosthesis

Two hundred and six consecutive total knee arthroplasties were performed in 180 patients with a highly congruous mobile-bearing knee prosthesis. At mean follow-up of 78 months (range: 60-102 months), the outcomes of 181 knees in 158 patients were evaluated using the American Knee Society's Knee and Functional scoring system and Radiological scoring system. Mean values for Knee and Function scores were 92.6 and 81.1, respectively versus 51.8 and 43.4 preoperatively; mean flexion range was 113.6 degrees versus 110.8 degrees preoperatively. There were no cases of bearing dislocation and no radiological signs of loosening or osteolysis. Secondary patella resurfacing was done in 7 of 52 knees in which the patella was not primarily resurfaced. Arthroplasty survival with revision for aseptic loosening as the endpoint was 100% (95% CI: 97.7-100) at 5 years and at 8 years (95% CI: 87.2-100); with revision of the arthroplasty for any reason including one revision for infection as the endpoint, survival was 99.5% (95% CI: 96.9-100) at 5 years and at 8 years (95% CI: 86.9-100). The overall results were satisfactory and compared with those of other mobile-bearing knee prostheses featuring full or partial congruence. No significant differences were noted for range of motion, knee scores and function scores between two subsets of knees that received a bearing allowing only rotation or rotation and 5 mm anteroposterior translation. Longer follow-up is needed to evaluate possible benefits of high congruence and of specific modes of bearing mobility with respect to wear and bony fixation.

Cemented total knee replacement in 24 dogs: surgical technique, clinical results, and complications

OBJECTIVE

To characterize the performance of cemented total knee replacement (TKR) in dogs.

STUDY DESIGN

Preclinical research study.

ANIMALS

Skeletally mature, male Hounds (25-30 kg; n=24) with no preexisting joint pathology.

METHODS

Dogs had unilateral cemented TKR and were evaluated at 6, 12, 26, or 52 weeks (6 dogs/time point) by radiography, bone density analysis, visual gait assessment, and direct measurement of thigh circumference and stifle joint range of motion as indicators of functional recovery. At study end, the stability of the cemented tibial component was determined by destructive mechanical testing.

RESULTS

Joint stability was excellent in 16 dogs (67%) and good in 8 dogs. None of the tibial components had evidence of migration or periprosthetic osteolysis whereas 1 femoral component was loose at 52 weeks. There was an early and significant decrease in tibial bone density, likely because of disuse of the operated limb. Dogs returned to full activity by 12 weeks. The tibial cement-bone interface maintained its strength over 52 weeks.

CONCLUSIONS

Cement provides stable fixation of the tibial component in canine TKR.

CLINICAL RELEVANCE

Cemented TKR yields adequate clinical function and stifle joint excursion in the dog. Clinical studies are needed to determine the long-term fate of cemented TKR implants, to assess the influence of implant design on implant fixation and wear, and to obtain objective functional data.

Significance of a "hot patella" in total knee replacement without primary patellar resurfacing

A "hot patella" is a bone scan finding of increased tracer uptake in the patella, greater than the ipsilateral distal femur or the proximal tibia. Increased patellar uptake on the bone scans is a relatively frequent finding; this is often not commented upon. The aim of our study was to define the incidence of a "hot patella" on bone scans following total knee replacements with ongoing symptoms unrelated to sepsis. We wanted to investigate the correlation between the adverse retropatellar symptomatology following total knee replacement with bone scan findings. We undertook a retrospective study of 55 symptomatic total knee replacement patients, who had bone scans. The incidence of a "hot patella" in patients without primary patellar resurfacing was 51% (28/55). Ninety-five percent patients with anterior knee pain and 21% patients with diffuse knee pain had a "hot patella". Statistical analysis showed a positive association between "hot patella" and anterior knee pain (p value of <0.001). The patients with "hot patella" who underwent secondary patellar resurfacing had symptomatic relief of symptoms. Our study has shown that the finding of a "hot patella" on a bone scan in patients with anterior knee pain following total knee replacement suggests a problem related to the patellofemoral joint. This study would appear to indicate that a "hot patella" in a patient with clinically defined anterior knee pain is likely to benefit from secondary patellar resurfacing.

Resurfacing versus nonresurfacing the patella in total knee arthroplasty: a critical appraisal of the available evidence

A systematic literature search for evidences comparing treatment effect and harm of resurfacing versus nonresurfacing the patella in total knee arthroplasty was conducted and yielded five meta-analysis (MA), one systematic review (SR) and six randomized controlled trials not included in previous MAs/SR. The evidence suggests that patellar resurfacing would reduce the risk of anterior knee pain, as well as the risk of patella-related reoperation. Furthermore, patients not undergoing patella resurfacing would experience more knee pain during stair climbing and be less satisfied with surgery. No significant difference in range of motion can be expected with or without patellar resurfacing. Importantly, methodological limitations were observed in all retrieved studies and evidences about potential adverse events related to patellar resurfacing are presently undetermined.

Routine patellar resurfacing using an inset patellar technique

The management of the patella in total knee arthroplasty still causes controversy. Whether or not to resurface the patella in primary total knee arthroplasty remains unclear. In this study we examined 220 consecutive total knee replacements, by a single surgeon, where the patella was routinely resurfaced using the inset technique. All patellae were suitable for resurfacing. Patellar thickness was not altered in 54.5% of patellae. In 97.2% the patella was within 2 mm of the original thickness. There were no significant complications. In this study we have found that the inset technique of patella resurfacing in total knee replacement is a simple and safe resurfacing procedure.

Ten-year results of an inset biconvex patella prosthesis in primary knee arthroplasty

The inset biconvex patella component is an alternative form of patella resurfacing in knee arthroplasty. We retrospectively reviewed 433 patients in whom 521 patella prostheses were implanted before April 1997 to determine survivorship, factors associated with failure of the implant, incidence of anterior knee pain, and factors that may be associated with the latter. We had clinical results for 204 surviving patients (242 knees) without failure of their implants with a minimum 10-year followup (mean, 11.4 years; range, 10-17 years). For the remaining 229 patients we used chart or radiographic review to determine if failure of their implant or other complications had occurred. At latest followup, 14 patella components had been revised for aseptic reasons or were radiographically loose. The 10-year Kaplan-Meier survivorship for the entire cohort for aseptic failure was 97.0%. Aseptic failure of the patella component was associated with the presence of osteonecrosis and the absence of a superior rim of bone radiographically. The incidence of anterior knee pain in surviving patients without failure of their implants was 7.8%. No factor examined was associated with anterior knee pain. Survivorship and clinical and radiographic results are equivalent, but not clearly superior, to those reported for other forms of patella resurfacing.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Differences in patellofemoral contact stresses between mobile-bearing and fixed-bearing total knee arthroplasties: a dynamic in vitro measurement

INTRODUCTION

Anterior knee pain is one of the most common problems after total knee arthroplasty (TKA). Mobile-bearing designs should improve patella tracking with a reduced rate of patella tilt as well as reduced patellofemoral contact stresses and improve knee flexion. The aim of this dynamic in vitro investigation was to evaluate the changes of patellofemoral contact stresses after TKA using fixed and mobile-bearing designs.

MATERIALS AND METHODS

Seven knee specimens were mounted into a knee simulator imitating an isokinetic extension of the knee. The patellofemoral contact was measured before and after tricompartimental TKA with fixed and mobile-bearing designs using pressure-sensitive films. Contact stresses were measured from 120 degrees knee flexion to full extension with a simulated force of the quadriceps muscle up to 1,200 N. Additionally all measurements were performed with simulated co-contraction of the hamstrings muscles.

RESULTS

Fixed-bearing TKA increases patellofemoral contact stresses compared to physiologic conditions. After patella resurfacing, contact stresses increase even more. By changing the prosthesis design to mobile bearing, maximum contact stress was measured to be punctual higher than in fixed-bearing implants. In the interval between 0 degrees -30 degrees and 70 degrees -105 degrees of flexion, obviously lower pressures were evaluated for the mobile-bearing design. With cocontraction of the hamstrings, a lower contact stress of the mobile-bearing design was evident for the complete measurement of the knee extension.

CONCLUSION

An increase of patellofemoral contact stresses after patellar resurfacing in TKA could be demonstrated. This outcome implicates a higher risk of patellofemoral complications. The mobile-bearing design showed evidently lower patellofemoral contact stresses than the fixed-bearing design.

Effect of an UHMWPE patellar component on stress fields in the patella: a finite element analysis

An increased stress in the patella due to the implantation of a patellar button may also be another potential source of pain in total knee arthroplasty patients. This study assessed the location inside the patella having largest stress change after implantation of an ultra high molecular polyethylene patella button. Finite elements models of the patellae before and after implantation of patellar button were created. Experimentally determined spring constants of muscles and ligaments, and patellofemoral contacting loads were applied to the models at 30 degrees , 60 degrees , and 90 degrees of knee flexion. The Von Mises stress of the intact patella decreased with increased knee flexion, while that of implanted patella increased. Also, the stress range in the implanted patella was 3-9 times higher than in the intact one. The highly stressed region of the intact patella moved proximally with higher knee flexion angles, while that of the implanted model stayed near the central anterior patella. At 90 degrees of knee flexion, the stress in the anterodistal patella increased considerably after implantation of a patella button so that the anterodistal patella may be susceptible to be painful source after the total knee replacement.

To resurface or not to resurface the patella in total knee arthroplasty

The management of the patellar articular surface at the time of primary total knee arthroplasty (TKA) is controversial. We used expected-value decision analysis to determine whether the patella should be resurfaced in TKA, and also whether secondary resurfacing on an unresurfaced patella is worthwhile. Outcome probabilities and utility values were derived from randomized controlled trials only. A decision tree was constructed and fold-back analysis was performed to ascertain the best treatment path. Sensitivity analyses were performed to determine the effect on decision-making of varying outcome probabilities and utilities. Our model showed patellar resurfacing is the best management strategy for the patella at the time of primary TKA. This decision is robust to changes in the specific data: the best path would remain the same as long as the incidence of persistent anterior knee pain (AKP) with resurfacing remains less than 29% (current mean, 12%) or the incidence of AKP after nonresurfacing falls below 12% (current mean, 26%). Delayed (ie, secondary) patellar resurfacing for ongoing patellar pain provides inferior results for the majority of patients.

LEVEL OF EVIDENCE

Level II, decision analysis. See the Guidelines for Authors for a complete description of levels of evidence.

Predicting patellar failure after total knee arthroplasty

We identified patient and surgeon factors associated with patellar component failure in a series of 8530 TKAs performed in 5640 patients using the same posterior cruciate ligament-retaining TKA with all-polyethylene patellar components between January 1983 and December 2003. Patellar failure was defined as loosening, fracture, or patellar revision. All infections were excluded. Statistical analysis using Kaplan-Meier and Cox regression was used to determine the risk of patellar failure. Followup averaged 7.0 years (range, 2-22 years). Patellar component loosening occurred in 4.8% of TKAs (409 knees). Patellar fracture was identified in 5.2% of TKA (444 knees). Twenty-five patellae were revised (0.3%). TKA performed with a lateral release and patients with a body mass index of greater than 30 kg/m(2) were at the greatest risk of patellar loosening and fracture, respectively. Male gender, preoperative varus alignment of greater than 5 degrees , and large patellar component size also predicted a higher risk of patellar fracture. Medial patellar component position, tibial component thickness of greater than 12 mm, preoperative valgus alignment of 10 degrees or more, and preoperative flexion of 100 degrees or more predicted patellar loosening. An awareness of these factors that predict patellar failure after TKA may help determine the relative indications for TKA and influence surgical technique, especially when using this prosthesis.

LEVEL OF EVIDENCE

Level IV, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Should the patella be resurfaced in primary total knee arthroplasty? An evidence-based analysis

Whether or not to resurface the patella in primary total knee arthroplasty remains controversial. Advocates for leaving the patella unresurfaced cite avoidance of complications that include patella fracture, avascular necrosis, patella tendon injury, and instability. Proponents of routine patella resurfacing cite the occasional need for secondary resurfacing procedures and the increased incidence of anterior knee pain in patients with unresurfaced patellae as a cause for concern with leaving a patella unresurfaced during knee arthroplasty. In addition, some advocate selective patellar resurfacing based on patient factors such as quality of the articular cartilage and patellofemoral congruence at the time of surgery. This review will discuss the available literature on patellar resurfacing through an evidence-based analysis.

Total knee replacement with and without patellar resurfacing: a prospective, randomised trial using the profix total knee system

We have examined the differences in clinical outcome of total knee replacement (TKR) with and without patellar resurfacing in a prospective, randomised study of 181 osteoarthritic knees in 142 patients using the Profix total knee system which has a femoral component with features considered to be anatomical and a domed patellar implant. The procedures were carried out between February 1998 and November 2002. A total of 159 TKRs in 142 patients were available for review at a mean of four years (3 to 7). The patients and the clinical evaluator were blinded in this prospective study. Evaluation was undertaken annually by an independent observer using the knee pain scale and the Knee Society clinical rating system. Specific evaluation of anterior knee pain, stair-climbing and rising from a seated to a standing position was also undertaken. No benefit was shown of TKR with patellar resurfacing over that without resurfacing with respect to any of the measured outcomes. In 22 of 73 knees (30.1%) with and 18 of 86 knees (20.9%) without patellar resurfacing there was some degree of anterior knee pain (p = 0.183). No revisions related to the patellofemoral joint were performed in either group. Only one TKR in each group underwent a re-operation related to the patellofemoral joint. A significant association between knee flexion contracture and anterior knee pain was observed in those knees with patellar resurfacing (p = 0.006).

Total knee arthroplasty for isolated patellofemoral arthritis in younger patients

Are the results of total knee arthroplasty for isolated patellofemoral osteoarthritis (OA) in younger patients as good as with patellofemoral arthroplasty? We retrospectively compared the outcomes of 33 TKAs in 27 patients with patellofemoral OA younger than 60 years of age (average, 52 years) to those for a matched group of patients with primarily tibiofemoral arthritis. A cemented posterior cruciate ligament-retaining prosthesis was used in 26 of the 27 knees. We recorded the intraoperative condition of the cartilage. Patients were followed a minimum of 2 years (average, 6.2 years). Average Knee Society knee scores improved from 49 preoperatively to 88 at final followup. Average pain scores from 5 to 44 with 29 knees rated with minimal or no pain; two patients reported anterior knee pain. There were no infections, revisions, reoperations, manipulations, patellar instabilities, patellar fractures, or component loosenings. The results in these patients were as good as those for younger historical control patients undergoing patellofemoral arthroplasty and the complication rates lower. The data were similar to those for our matched group of patients with primarily tibiofemoral OA. We believe our data should raise doubts about the use of patellofemoral arthroplasty in any patient.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Patellofemoral instability after total knee arthroplasty

Despite advances in surgical technique and implant design, complications involving the extensor mechanism and patellofemoral joint after total knee arthroplasty (TKA) continue to be the most common cause of pain and the most commonly cited reason for revision TKA surgery. A thorough understanding of the etiologies of patellofemoral instability, careful preoperative planning, and meticulous surgical techniques will optimize clinical outcome. Evaluation of patellofemoral stability should begin in the operating room. Postoperatively, thorough history, physical examination, and dedicated radiographic studies should be obtained. Computed tomography scan is the most accurate and reliable way to assess component positioning. Treatment of patellofemoral instability is directed by its etiology. Revision of one or both components is indicated if malpositioning is present. If the components are determined to be in satisfactory positions, soft tissue procedures can be pursued. Future advancements in prosthetic design and the routine use of computer-assisted navigation systems will minimize patellofemoral instability.

LEVEL OF EVIDENCE

Therapeutic study, Level V (expert opinion). See the Guidelines for Authors for a complete description of levels of evidence.