Immediate or late weight bearing after uncemented total hip arthroplasty: a study of functional recovery

Walk-IT: An Open-Source Modular Low-Cost Smart Rollator

Rollators are widely used in clinical rehabilitation for gait assessment, but gait analysis usually requires a great deal of expertise and focus from medical staff. Smart rollators can capture gait parameters autonomously while avoiding complex setups. However, commercial smart rollators, as closed systems, can not be modified; plus, they are often expensive and not widely available. This work presents a low cost open-source modular rollator for monitorization of gait parameters and support. The whole system is based on commercial components and its software architecture runs over ROS2 to allow further customization and expansion. This paper describes the overall software and hardware architecture and, as an example of extended capabilities, modules for monitoring dynamic partial weight bearing and for estimation of spatiotemporal gait parameters of clinical interest. All presented tests are coherent from a clinical point of view and consistent with input data.

Total Hip Arthroplasty in Patients With Sickle Cell Disease: A Comprehensive Systematic Review

BACKGROUND

Total hip arthroplasty (THA) is a common treatment for end-stage osteonecrosis of the hip in patients with sickle cell disease (SCD). This patient population presents unique challenges in the perioperative period. This systematic review aims to investigate the existing literature on the outcomes, complications, and survivorship of primary THA in SCD patients.

METHODS

A systematic search using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines was performed of PubMed, MEDLINE, EMBASE, and Cochrane databases for clinical studies on THA in SCD patients. Studies on primary THA in SCD patients with a mean follow-up greater than 90 days were included.

RESULTS

Sixteen studies containing 5193 SCD patients met criteria for inclusion. The Coleman Quality of Evidence score ranged from poor to moderate. SCD patients had a significant increase in Harris Hip Scores and Merle d'Aubigne Scores after undergoing THA. Compared to non-SCD patients, SCD patients had increased hospital length-of-stay, 30-day and 90-day readmission rates, and rates of medical complications, including pain crises, acute chest syndrome, cardiac complications, sepsis, and mortality. SCD patients also had increased rates of surgical complications, including wound complications, infection, periprosthetic fracture, and aseptic loosening. Overall, THA revision rates were higher in SCD patients relative to those with primary osteoarthritis.

CONCLUSION

THA remains an effective treatment modality for osteonecrosis of the hip in SCD patients. However, these patients are at increased risk of medical and surgical complications. Surgeons should be aware of the unique challenges in this patient population when counseling and managing these patients in the perioperative period.

Perioperative platelet rich plasma (PRP) in total hip arthroplasty through the Hardinge approach: protocol to study the effectiveness for gluteus medius healing

Background

Platelet-rich plasma (PRP) has been used to support tendon regeneration mainly in sports medicine. PRP is a concentrate of platelet-rich plasma proteins derived from whole blood by centrifugation to remove erythrocytes and leukocytes. PRP has high amounts of platelets which may promote healing tendons affected by degenerative conditions. These platelets contain growth factors and are known to facilitate the regeneration of injured tendon structures. Total hip arthroplasty (THA) through the Hardinge approach may leave the patient with impaired gait and poor regeneration of the gluteus medius tendon if the tendon is not reattached properly after closure of the surgical wound.

Methods

The study will be a multicenter, double-blinded and randomized study enrolling 90 patients based on power calculations. The efficacy of perioperative PRP treatment will be assessed by subjective and objective outcome variables. The participants will be randomized (sealed envelope) into either a placebo (saline) or a PRP group (1:1). For subjective outcomes, the Oxford Hip Score (OHS) will be collected before surgery and 3 and 12 months after surgery. The objective measures are findings at magnetic resonance imaging and plain radiographs and recorded values of measured strength.

Discussion

We present the perioperative use and the ways to measure the clinical efficacy of PRP. As PRP may have benefits regarding degenerative tendon regeneration, studies on the use of PRP in hip arthroplasty are warranted to facilitate postoperative recovery.

Trial registration

This study has been approved by the ethics committee of the Hospital District of Southwest Finland and approved by the local institutional research board. The study has been registered in ClinicalTrials.gov (NCT02607462).

Does the Dual-Mobility Hip Prosthesis Produce Better Joint Kinematics During Extreme Hip Flexion Task?

BACKGROUND

Total hip arthroplasty (THA) using dual-mobility (DM) design permits larger hip range of motion. However, it is unclear how it benefits the patients during activities of daily living. The purpose was to compare kinematic variables of the operated limb between THA patients using either DM or single-bearing (SB) implants during a squat task.

METHODS

Twenty-four THA patients were randomly assigned to either a DM or SB implant and matched to 12 healthy controls (CTRLs). They underwent 3-dimensional squat motion analysis before and 9 months after surgery. Sagittal and frontal plane angles of the pelvis and the hip were analyzed using statistical parametric mapping. Paired analyses compared presurgery and postsurgery squat depth.

RESULTS

Peak sagittal pelvis angle of DM was closer to normal compared with that of SB. Both implant groups had similar hip angle patterns and magnitude but significantly lower than the CTRLs. SB reached a much large hip abduction compared with the other groups. Both surgical groups had significantly worst squat depth than the CTRLs.

CONCLUSION

Neither THA implant groups were able to return pelvis and hip kinematics to the level of CTRLs. The deficit of DM implants at the pelvis combined with the poorer functional scores should caution clinicians to use this implant design in active patients. SB design causes a larger hip abduction to reach their maximum squat depth. Post-THA rehabilitation should focus on improving joint range of motion and strength.

Partial versus early full weight bearing after uncemented total hip arthroplasty: a meta-analysis

BACKGROUND

This meta-analysis aimed to investigate the efficacy and safety of partial weight bearing (PWB) versus early full weight bearing (FWB) after uncemented total hip arthroplasty (THA).

METHODS

We conducted a search in PubMed, EMBASE, The Cochrane Library, and Web of Science for randomized controlled trials (RCTs) and non-RCTs comparing PWB and early FWB after uncemented THA. Two authors conducted the selection of studies, data extraction, and assessment of risk of bias independently. A pooled meta-analysis was performed using the RevMan 5.3 software.

RESULTS

Six RCTs and three non-RCTs met the inclusion criteria. The meta-analysis indicated that compared with PWB, the FWB group showed greater femoral subsidence at 3-month follow-up (MD = -0.12, 95% CI -0.22 to -0.01, P = 0.03). There were no significant differences in the hip Harris score at 1-year and 2-year follow-up (MD = 1.54, 95% CI -0.83 to 3.90, P = 0.20; MD = 0.08, 95% CI -1.19 to 1.34, P = 0.90, respectively), in femoral subsidence at 2-year follow-up and at two additional years of follow-up (MD = -0.03, 95% CI -0.31 to 0.25, P = 0.84; (MD = -0.02, 95% CI -0.37 to 0.33, P = 0.91, respectively). There were no significant differences in the incidences of bone ingrowth fixation, spot welds, and radiolucent lines.

CONCLUSIONS

This meta-analysis shows that early FWB in patients with uncemented THA could be safe and could not increase the incidence of postoperative complications.

[Rehabilitation after hip and knee endoprosthetic treatment in the elderly]

Due to current demographic developments with a continuous increase in average life expectancy and improved medical treatment, the number of elderly patients with joint replacement of the lower extremities also has increased in recent years. Most of these patients have not only one but several chronic diseases requiring treatment and medication. Drug-drug interaction and functional restrictions of the elderly additionally reduce the postoperative psychophysical capacity; therefore, special knowledge in rehabilitative treatment and pain management is necessary. Physiotherapy and exercise should include training of mobility, endurance, strength, coordination and training in activities of daily living. The individual constitution and pain during exercise must always be taken into consideration. Rehabilitative outcome is dependent on a functioning cooperation of an interdisciplinary rehabilitation team and requires an organized, holistic treatment approach in interconnected structures, which aims at rapid postoperative mobilization.

Factors associated with restricted hip extension during gait in women after total hip arthroplasty

PURPOSE

A decreased peak hip extension angle in the late stance phase is a major gait abnormality in patients with THA. The purpose of this study was to determine the relationship between peak hip extension angle during gait and functional impairments such as muscle weakness and the limitation in joint range of motion and to identify the clinical factors influencing peak hip extension angle during gait.

METHODS

67 female volunteers with THA were examined. Biomechanical gait analysis was performed to measure peak hip extension angle during gait. Maximal isometric strength of the hip and knee, passive hip extension range of motion, leg length discrepancy, and hip pain were assessed.

RESULTS

Peak hip extension angle during gait significantly correlated with passive hip extension range of motion (r = 0.259), hip pain (r = -0.264), isometric strengths of the hip musculature (r = 0.278-0.491), and knee extensor (r = 0.386). Stepwise multiple regression analysis revealed that hip abductor torque (β = 0.355, P = 0.001), hip pain (β = -0.353, P = 0.001), and passive hip extension range of motion (β = 0.258, P = 0.011) were significant contributors to peak hip extension angle during gait (R2 = 0.408).

CONCLUSIONS

Our findings suggest that THA rehabilitation aimed at improving gait ability should focus on strengthening the hip abductors, controlling hip pain and increasing range of motion of hip extension.

Unrestricted Weight Bearing and Intensive Physiotherapy after Uncemented Total Hip Arthroplasty

Background and Aims:

The effectiveness of partial weightbearing after hip surgery has been questioned as well as the need of intensive physiotherapy.

Material and Methods:

36 patients (average age 54.4, 19 women) operated with uncemented hip arthroplasty were randomized either to unrestricted weightbearing (UWB) combined with intensive physiotherapy or to partial weightbearing (PWB) for 3 months combined with a short self-training program. The load during walking and the muscle strength (MS) in abduction was measured preoperative and subsequent up to 12 months.

Results:

The average peak load on the operated leg at one week was 39.0 kg for the UWB and 25.8 for the PWB group (P = 0.009) while at three months 70.0 and 31.7 (P = 0.001) respectively. At 6 and 12 months there were no differences between the groups. The muscle strength increased in both groups up to six months but there were no differences between the groups.

Conclusions:

Even though patients applied more load than the recommended 15 kg most patients were able to comply with partial weightbearing fairly well. The effect of intensive physiotherapy on the muscle strength after hip arthroplasty is questionable.

Task-oriented exercises and early full weight-bearing contribute to improving disability after total hip replacement: a randomized controlled trial

OBJECTIVE

To evaluate the efficacy of an in-hospital programme based on task-oriented exercises associated with early full weight-bearing in patients with multiple comorbidities undergoing total hip replacement.

DESIGN

Randomized controlled trial.

SETTING

Specialised rehabilitation centre.

SUBJECTS

A total of 100 patients (mean age of 69 (8) years; 40 males, 60 females).

INTERVENTIONS

The experimental group underwent task-oriented exercises and was encouraged to abandon any walking aids by the end of their in-hospital stay. The control group underwent open chain kinetic exercises, and was recommended to use partial weight-bearing and walking aids until three months after surgery. Both groups individually followed programmes of 90-minute sessions five times a week for three weeks.

OUTCOME MEASURES

Western Ontario and McMaster Universities Osteoarthritis Index, Pain Numerical Rating Scale, Functional Independence Measure, and Short-Form Health Survey. The participants were evaluated before, after training, and after a further 12 months.

RESULTS

There were no significant between-group differences at baseline. After training, a between-group difference of 12 points was found for the Western Ontario and McMaster Universities Osteoarthritis Index - functional subscale, indicating a clinically tangible treatment effect on disability. The Functional Independence Measure increased by 31 and 15 points in the experimental and control group, respectively. A linear mixed model revealed significant effects of time, group, and time by group interaction on disability, pain, activities of daily living, and most of the physical quality of life domains.

CONCLUSION

Task-oriented exercises associated with early full weight-bearing improve disability, pain, activities of daily living, and quality of life after total hip replacement.

Effect of immediate full weight bearing on abductor repair and clinical function after THA through a modified Hardinge approach

This study evaluated the effect of immediate full weight bearing on abductor repair and clinical function after total hip arthroplasty (THA) using a direct lateral (modified Hardinge) approach. The surgical approach detached a bone flake with the abductors, providing a radiographic marker for abductor displacement and healing. Patients in whom weight bearing was restricted for 6 weeks (partial-weight bearing group) were compared with patients who were immediately weight bearing (full-weight bearing group). A total of 307 patients (309 hips) were followed for a mean of 14 months (range, 12-36 months). The partial-weight bearing group (163 patients) underwent 6 weeks of partial weight bearing, and the full-weight bearing group (146 patients) underwent immediate full weight bearing. The abductor repair was assessed radiographically via the bone flake harvested with abductor muscles. Nonunion of the abductor bone was observed in 12 (7%) patients in the partial-weight bearing group and 9 (6%) patients in the full-weight bearing group (P=.55). Patients in the full-weight bearing group had significantly earlier discharge from hospital than the partial-weight bearing group (2.6 vs 3.5 months, respectively; P=.0021). Patients in the full-weight bearing group had a higher mean Engh score (6.58) radiographically than did patients in the partial-weight bearing group (4.92) (P=.0005). No difference was observed in Harris Hip Score, limp, thigh pain, high-grade heterotopic bone, trochanteric bursitis, or stem subsidence between groups. Restricting weight bearing postoperatively to protect the Hardinge abductor repair appears unnecessary, and recovery of activity is improved with immediate weight bearing.

Post-operative gait analysis in total hip replacement patients-a review of current literature and meta-analysis

Gait analysis has been used to measure gait adaptations following total hip replacement (THR) for many years. In this time, advances have been made in implant technology and surgical procedure. However, gait adaptations persist after surgery. This review of seven published studies, where gait characteristics were compared between post-operative THR patients and healthy controls, had the objective of investigating current practice in gait analysis of this patient population and to determine if there is a consensus on post-operative gait changes associated with THR. Levels of methodological quality and study design were found to be variable. Meta-analyses were performed on all gait variables reported by at least three studies to determine overall Cohen's d effect sizes and 95% confidence intervals. Reductions in walking velocity (d=-0.79; CI=-1.54, -0.04), stride length (d=-1.06; CI=-1.62, -0.49) and sagittal hip range of motion (d=-1.58; CI=-2.12, -1.04) were observed. Increases in peak hip flexion (d=0.52; CI=-0.01, 1.09) and extension (d=0.54; CI=-0.10, 1.09) moments were found, although these were likely to be of less clinical significance. Reduced peak hip abduction was also observed (d=-0.58; CI=-1.09, -0.06). Future developments in THR technology and surgical methods should therefore aim to reduce the differences between patients and controls in terms of walking velocity, stride length, hip range of motion and hip abduction moments.

Gait symmetry: a comparison of hip resurfacing and jumbo head total hip arthroplasty patients

Proponents of large femoral head total hip arthroplasty (THA) and hip resurfacing arthroplasty (HRA) have touted the potential for restoration of more normal hip kinematics. This study examined 20 patients (10 THA and 10 HRA patients) approximately 18 months after surgery. Subjects were evaluated at a self-selected pace, while bilateral spatial-temporal gait variables, hip flexion/extension kinematics, and ground reaction forces were collected. For both groups, swing time was increased on the surgical side, whereas peak hip flexion, peak extension, and flexion at heel strike were decreased. Peak hip extension and peak vertical ground reaction forces were decreased in THA subjects compared with HRA subjects. After a large-diameter THA or HRA, subjects do not display symmetric gait approximately 18 months postoperatively. Total hip arthroplasty subjects demonstrated restricted hip extension and reduced limb loading when compared with HRA subjects.

Partial versus unrestricted weight bearing after an uncemented femoral stem in total hip arthroplasty: recommendation of a concise rehabilitation protocol from a systematic review of the literature

The aim of this systematic review was to find evidence-based support in the literature to allow immediate unrestricted weight bearing after primary uncemented total hip arthroplasty (THA). Accelerated rehabilitation programs for THA are becoming increasingly popular to shorten hospital stay and to facilitate rapid restoration of function. The goals of these rehabilitation programs could be more easily achieved if immediate unrestricted weight bearing (UWB) could be allowed after a THA. So far, however, immediate weight bearing is frequently contraindicated in widely accepted protocols for uncemented THA due to fear for subsidence and absence of osseous integration of the femoral stem. Thus, frequently protected weight bearing and restricted activities are still advocated for at least 6 weeks after surgery. In addition, we analyzed the literature to come to a recommendation on gait pattern and walking aid. From a systematic search in several electronic databases 13 studies met the inclusion criteria. These studies were reviewed according to the Cochrane methodology. We found moderate to strong evidence that no adverse effects on subsidence and osseous integration of the femoral stem after uncemented THA occur after immediate UWB. Based on this literature review, we recommend early rehabilitation after uncemented THA with a reciprocally gait pattern using crutches, one cane for independency in ADL in case patients walk limp-free and walking without crutches as soon as possible. During the first weeks after surgery only stair climbing should be performed with protected weight bearing because of high torsion loads on the hip.

No adverse effects of early weight bearing after uncemented total hip arthroplastyA randomized study of 20 patients

BACKGROUND

Few guidelines are available whether early weight-bearing after an uncemented total hip arthroplasty (THA) can be recommended or not. Stability and ingrowth may be jeopardized by immediate loading of the implant while functional recovery may be promoted and periprosthetic demineralization reduced.

PATIENTS AND METHODS

We did a prospective study of 20 patients who were operated on with a hydroxyapatite-coated (HA), uncemented total hip arthroplasty with a tapered stem because of unilateral arthrosis, and randomized the patients to the immediate (I) or late (L) weight-bearing (after 3 months) group. The shoe on the operated side was equipped with an auditory device signaling when the patient placed a load on the extremity. The clinical assessment was done with the Harris hip score at the time of the operation and after 12 and 24 months. Radiographs and dual-energy x-ray absorptiometry (DEXA) were evaluated for migration, femoral remodeling and bone mineral density (BMD) after 3, 6, 12 and 24 months. Tc-scintigraphy was done after 6, 12 and 24 months.

RESULTS

Postoperatively, the Harris hip score showed no group difference. After 3 months, we noted a large reduction in BMD around the stem prosthesis. This was most marked in the proximal regions and the bone loss was significantly larger in zone 1, 4 and 5 in the L group. Distally, the BMD normalized with time, but the loss of bone persisted in the proximal zones after 24 months. An initial increase in the scintigraphic uptake ratio in all zones in both groups declined with time, but it was still increased on the operated side after 24 months. Several radiographic signs of bone remodeling were seen, but the patterns were similar in both groups.

INTERPRETATION

We found no adverse effect of immediate weight bearing with this prosthesis.

Gait and stair function in total and resurfacing hip arthroplasty: a pilot study

Standard total hip arthroplasty (THA) is the established surgical treatment for patients older than 65 years with progressive osteoarthritis but survivorship curves wane in patients younger than 50. Resurfacing hip arthroplasty (RHA) is an alternative for younger, active patients reportedly providing superior range of motion. Quantitative investigation of functional recovery following arthroplasty may elucidate limitations that aid in device selection. Although limited long-term kinematic data are available, the early rate of recovery and gait compensations are not well described. This information may aid in refining rehabilitation protocols based on limitations specific to the implant. We presumed hip motion and forces for subjects receiving RHA are more similar to age-matched controls during physically demanding tasks, such as stair negotiation, at early time points than those for THA. In a pilot study, we quantified walking and stair negotiation preoperatively and 3 months postoperatively for seven patients with RHA (mean age, 49 years), seven patients with standard THA (mean age, 52 years), and seven age-matched control subjects (mean age, 56 years). Although both treatment groups demonstrated trends toward functional recovery, the RHA group had greater improvements in hip extension and abduction moment indicating typical loading of the hip. Further investigation is needed to determine if differences persist long term or are clinically meaningful.

Immediate weight bearing after cementless total hip arthroplasty

This study analyzed 399 Balance femoral stems to determine whether immediate full weight bearing following total hip arthroplasty affected radiographic osseointegration. Postoperatively, all patients were permitted unlimited weight bearing. Findings demonstrated osseointegration was successful in 99.5% of femoral components. Of these, 0.5% subsided in the first 6 postoperative weeks and then osseointegrated; 0.5% failed to osseointegrate. Patients with Dorr C bone had a significantly increased rate of subsidence (P=.006). These findings indicate the Balance stem reliably osseointegrates without subsidence in patients with Dorr A or B bone, despite immediate full weight bearing.

Immediate weight bearing after uncemented total hip arthroplasty with an anteverted stem: a prospective randomized comparison using radiostereometry

BACKGROUND

In uncemented total hip arthroplasty with hydroxyapatite coating, early weight bearing is frequently practiced but there is still not much evidence to support this recommendation.

METHOD

In a prospective randomized study we evaluated the effect of partial and full weight bearing after cementless total hip arthroplasty (ABG; Stryker-Howmedica) using radiostereometric analysis (RSA). Between February 1996 and February 2000, 43 consecutive patients (mean age 53 (41-63) years, 23 women) with hip osteoarthrosis received an uncemented and hydroxyapatite-coated prosthesis with an anteverted stem. All patients were operated in a standardized way by three experienced surgeons and they were randomized to partial (P) or full (F) weight bearing during the first 6 weeks after surgery. The patients in the partial weight bearing group were equipped with a pressuresensitive insole signaling when their load exceeded the prescribed weight limit.

RESULTS

At 3-month follow-up, the mean proximal (+)/ distal (-) migration of the stem was -0.14 mm (-1.93- 0.11) in group P and -0.31 mm (-4.30-0.16) in group F (p=0.6). At 1-year follow-up, the mean migration was -0.17 mm (-2.18-0.21) and -0.28 mm (-4.31-0.11), respectively (p=0.9). There was no significant difference in stem rotations either (p<0.2). The cup translations, rotations, and femoral head penetration were similar in the two groups (p<0.1). There were no re-operations during the first year.

INTERPRETATION

We did not find any adverse effect of full weight bearing immediately after operation, which justifies use of this regimen after uncemented total hip arthroplasty of the ABG type.

Gait analysis of patients with resurfacing hip arthroplasty compared with hip osteoarthritis and standard total hip arthroplasty

Patients with standard total hip arthroplasties may have reduced hip abduction and extension moments when compared with normal nonosteoarthritic hips. In comparison, patients after resurfacing total hip arthroplasty appear to have a near-normal gait. The authors evaluated temporal-spatial parameters, hip kinematics, and kinetics in hip resurfacing patients compared with patients with unilateral osteoarthritic hips and unilateral standard total hip arthroplasties. Patients with resurfacing walked faster (average 1.26 m/s) and were comparable with normals. There were no significant differences in hip abductor and extensor moments of patients with resurfacing compared with patients in the standard hip arthroplasty group. This study showed more normal hip kinematics and functionality in resurfacing hip arthroplasty, which may be due to the large femoral head.

Rapid rehabilitation and recovery with minimally invasive total hip arthroplasty

To assess the potential recovery rate of a minimally invasive total hip replacement technique with minimal soft tissue disruption, an accelerated rehabilitation protocol was implemented with weightbearing as tolerated on the day of surgery. One hundred consecutive patients were enrolled in this prospective study. Ninety-seven patients (97%) met all the inpatient physical therapy goals required for discharge to home on the day of surgery; 100% of patients achieved these goals within 23 hours of surgery. Outpatient therapy was initiated in 9% of patients immediately, 62% of patients by 1 week, and all patients by 2 weeks. The mean time to discontinued use of crutches, discontinued use of narcotic pain medications, and resumed driving was 6 days postoperatively. The mean time to return to work was 8 days, discontinued use of any assistive device was 9 days, and resumption of all activities of daily living was 10 days. The mean time to walk (1/2) mile was 16 days. Furthermore, there were no readmissions, no dislocations, and no reoperations. Therefore, a rapid rehabilitation protocol is safe and fulfills the potential benefits of a rapid recovery with minimally invasive total hip arthroplasty.

Tibio-femoral loading during human gait and stair climbing

Surgical intervention of the knee joint routinely endeavors to recreate a physiologically normal joint loading environment. The loading conditions resulting from osteotomies, fracture treatment, ligament replacements, and arthroplasties of the knee are considered to have an impact on the long term clinical outcome; however, knowledge regarding in vivo loading conditions is limited. Using a previously validated musculoskeletal lower limb model, we predicted the tibio-femoral joint contact forces that occur in the human knee during the common daily activities of walking and stair climbing. The average resultant peak force during walking was 3.1 times body weight (BW) across four total hip arthroplasty patients. Inter-individual variations proved larger than the variation of forces for each patient repeating the same task. Forces through the knee were considerably larger during stair climbing than during walking: the average resultant peak force during stair climbing was 5.4 BW although peaks of up to 6.2 BW were calculated for one particular patient. Average anteroposterior peak shear components of 0.6 BW were determined during walking and 1.3 BW during stair climbing. These results confirm both the joint contact forces reported in the literature and the importance of muscular activity in creating high forces across the joint. The magnitudes of these forces, specifically in shear, have implications for all forms of surgical intervention in the knee. The data demonstrate that high contact and shear forces are generated during weight bearing combined with knee flexion angles greater than approximately 15 degrees. Clinically, the conditions that produce these larger contact forces should be avoided during post-operative rehabilitation.

How accurate is partial weightbearing?

The accuracy of partial weightbearing was assessed in six healthy volunteers and 23 patients who had sustained either a fracture of a lower limb or surgery. They were trained to weightbear partially using the conventional bathroom scale method and were assessed in a gait laboratory using force platforms. The amount of weight exerted on the involved limb during three-point crutch walking was determined. Four of six volunteers exerted a mean of 27% of body weight more than required. The remaining two volunteers exerted a mean of 8.5% of body weight less than required. Of the 23 patients, 21 exerted a mean of 35.3% of body weight more than that prescribed and two patients exerted a mean of 11.97% of body weight less than that prescribed. In both groups there was little relationship between the weightbearing prescribed and actual weightbearing. None of the patients or volunteers was able to reproduce the extent of partial weightbearing for which they were trained using the bathroom scale method, confirming that this technique of instructing patients in partial weightbearing is inaccurate.