The Development and Biomechanical Analysis of an Allograft Interference Screw for Anterior Cruciate Ligament Reconstruction

Graft fixation during cruciate ligament reconstruction using interference screws is a common and frequently used surgical technique. These interference screws are usually made of metal or bioabsorbable materials. This paper describes the development of an allograft interference screw from cortical human bone. During the design of the screw, particular attention was paid to the choice of the screw drive and the screw shape, as well as the thread shape. Based on these parameters, a prototype was designed and manufactured. Subsequently, the first biomechanical tests using a bovine model were performed. The test procedure comprised a torsion test to determine the ultimate failure torque of the screw and the insertion torque during graft fixation, as well as a pull-out test to asses the ultimate failure load of the graft fixation. The results of the biomechanical analysis showed that the mean value of the ultimate failure torque was 2633 Nmm, whereas the mean occurring insertion torque during graft fixation was only 1125 Nmm. The mean ultimate failure load of the graft fixation was approximately 235 N. The results of this work show a good overall performance of the allograft screw compared to conventional screws, and should serve as a starting point for further detailed investigations and studies.

Electrocautery Damage Can Reduce Implant Fatigue Strength: Cases and in Vitro Investigation

BACKGROUND

The risk of femoral stem fracture after total hip replacement is low and can often be associated with a specific implant system or other factors that may reduce the fatigue strength. Additionally, damage to a metal component during revision surgery by an electrocautery device may further affect the fatigue behavior.

METHODS

Two clinical cases of stem failure after revision of fractured ceramic components are presented; the retrieved components were analyzed for the cause of failure. In vitro cyclic load-to-failure testing of titanium alloy femoral stems after electrocautery application at 2 different locations (at the base and about midway on the femoral neck) was performed using a stepwise increase in load until implant fracture occurred. In addition, a detailed characterization of the local material structure around the electrocautery marks was performed.

RESULTS

Superficial discoloration and melting marks were found on the retrieved components, including at the location of crack initiation in the anterolateral region, which may have reduced the fatigue strength of the material. In addition, elemental analysis indicated material transfer from the electrocautery tip. Damage to the surface by the electrocautery device significantly reduced the in vitro load to failure by up to 47% compared with that of undamaged femoral neck specimens. Material analysis revealed a relevant modification in microstructure, with an extension of approximately 2.7 mm and a depth of 550 µm, which could be divided in 3 structural zones.

CONCLUSIONS

Intraoperative electrocautery device contact with the implant during surgical revision of a total hip replacement cannot always be avoided. However, on the basis of our findings, the risk of implant failure is increased due to a change in microstructure and a potential reduction of the implant's fatigue strength. Surgeons and manufacturers of electrocautery devices should be aware of this concern.

CLINICAL RELEVANCE

During revision surgery, contact between an electrocautery device and the femoral component should be avoided to reduce the chance of subsequent femoral neck fracture.

MR arthrography of the hip with and without leg traction: Assessing the diagnostic performance in detection of ligamentum teres lesions with arthroscopic correlation

OBJECTIVES

To retrospectively assess the diagnostic performance of hip MR arthrography with and without traction in detecting ligamentum teres (LT) lesions with arthroscopic correlation and to evaluate the effect of traction on the imaging appearance of the LT.

METHODS

73 MR arthrograms (73 consecutive patients, mean age, 34.5 years; range, 14-55 years) obtained without and with leg traction (application of 15-23 kg, use of a supporting plate for the contralateral leg) were included. Two blinded readers independently evaluated LT lesions on MR arthrograms on separate occasions: coronal images without traction; coronal images with traction; a multiplanar traction protocol. MR findings were correlated with arthroscopic records. Sensitivity/specificity of traction and non-traction imaging was compared on coronal images with the exact McNemar test. Imaging appearance of the LT with and without traction was assessed in consensus and compared on coronal images using McNemar and McNemar-Bowker tests. (p<0.05, * corrected for type I error).

RESULTS

With arthroscopy 29 (40%) LT lesions were identified in 73 patients. Sensitivity was 72%/90% (without traction/with traction; p=0.25*), specificity was 89%/77% (p=0.25*) for reader 1 in assessing coronal images and for reader 2 sensitivity was 59%/86% (p=0.044*) and specificity was 93%/82% (p=0.25*). Alterations in fiber orientation, signal intensity, surface, dimension, fiber continuity after application of traction were observed in 33/73 (45%, p=0.002*), 6/73 (8%, p=0.223), 9/73 (12%, p=0.36*), 6/73 (8%, p=0.031) respectively 9/73 (12%, p=0.003) cases. Traction-related alterations in at least one criterion were observed in 41/73 (56%) cases.

CONCLUSION

Application of traction can considerably alter the imaging appearance of the LT and resulted in higher rates of true-positive and false-positive findings compared to conventional MR arthrography.

Diagnostic performance of direct traction MR arthrography of the hip: detection of chondral and labral lesions with arthroscopic comparison

OBJECTIVES

To assess diagnostic performance of traction MR arthrography of the hip in detection and grading of chondral and labral lesions with arthroscopic comparison.

METHODS

Seventy-five MR arthrograms obtained ± traction of 73 consecutive patients (mean age, 34.5 years; range, 14-54 years) who underwent arthroscopy were included. Traction technique included weight-adapted traction (15-23 kg), a supporting plate for the contralateral leg, and intra-articular injection of 18-27 ml (local anaesthetic and contrast agent). Patients reported on neuropraxia and on pain. Two blinded readers independently assessed femoroacetabular cartilage and labrum lesions which were correlated with arthroscopy. Interobserver agreement was calculated using κ values. Joint distraction ± traction was evaluated in consensus.

RESULTS

No procedure had to be stopped. There were no cases of neuropraxia. Accuracy for detection of labral lesions was 92 %/93 %, 91 %/83 % for acetabular lesions, and 92 %/88 % for femoral cartilage lesions for reader 1/reader 2, respectively. Interobserver agreement was moderate (κ = 0.58) for grading of labrum lesions and substantial (κ = 0.7, κ = 0.68) for grading of acetabular and femoral cartilage lesions. Joint distraction was achieved in 72/75 and 14/75 hips with/without traction, respectively.

CONCLUSION

Traction MR arthrography safely enabled accurate detection and grading of labral and chondral lesions.

KEY POINTS

• The used traction technique was well tolerated by most patients. • The used traction technique almost consistently achieved separation of cartilage layers. • Traction MR arthrography enabled accurate detection of chondral and labral lesions.

Improving visualization of the central compartment of the hip with direct MR arthrography under axial leg traction: a feasibility study

RATIONALE AND OBJECTIVES

To evaluate the feasibility of a modified approach for direct magnetic resonance (MR) arthrography of the hip under leg traction in achieving a sufficient femoroacetabular interface and improving the visualization of the ligamentum teres.

MATERIALS AND METHODS

Forty-six MR arthrograms of 44 patients who underwent MR arthrography with and without leg traction were included into the study. Traction approach included injection of 18-27 mL of fluid (local anesthetic, contrast agent), application of weight-adapted traction load (15-23 kg), and the use of a supporting plate. Patients were instructed to report on pain and complications with an integer pain scale. Joint distraction was measured on coronal images obtained with and without traction, and two radiologists independently evaluated whether femoroacetabular cartilage layers and the ligamentum teres could be seen as distinct entities. McNemar test was used and interobserver agreement was assessed.

RESULTS

No patient asked for termination of the examination. There were no cases of neuropraxia. Mean difference in distraction was 3.7 mm/3.6 mm (reader 1/reader 2). Cartilage layers could be seen as distinct entities in 43/43 (93.5%/93.5%) and 6/8 (13%/17.4%) of the joints with/without traction (P < .001/P < .001), respectively. The ligamentum teres could be differentiated in 33/30 (71.7%/65.2%) cases with traction, in 33/30 (71.7%/65.2%) cases without traction (P < .999/P < .999), and in 40/37 (87%/80.4%) cases with both the techniques combined.

CONCLUSIONS

Traction MR arthrography is safe and technically feasible. It enabled the differentiation between femoroacetabular cartilage layers in most cases. Visualization of the ligamentum teres was optimal by combining imaging with both modalities.

[Capacity to participate in sports after injuries of the acromioclavicular joint]

In 79 patients athletic activities were evaluated retrospectively 32 months after grade II and grade III sprains of the acromioclavicular joint. Group I consisted of 29 patients with grade II sprains according to Tossy and group II consisted of 50 patients with grade III sprains according to Tossy. In group Ia 14 patients underwent surgery, and in group Ib 15 patients were treated nonsurgically. In group IIa 41 patients were treated surgically, and in group IIb 9 patients were treated conservatively. Forty-seven patients were injured during participation in sports. Among these 16 were injured during participation in their specific sport. In group I patients had to curtail sports activities more frequently after surgery than after conservative treatment (p < 0.05). In group II the reduction of sports activities was not different for the two treatment groups. Of a total of 79 patients, 23 had to reduce their sports activities. Among these, 7 patients had to give up sports. All patients had performed overhead athletic activities. Climbers and patients performing strength training had to reduce their activities or give up sports. Additionally, sprains of the acromi-oclavicular joint adversely affected athletic activities in overhead ball sports, bicycling, and skiing irrespective of treatment.

[Computer-assisted drilling of the lower extremity. Technique and indications]

Computer assisted navigation-based surgery is a novel and interesting challenge for todays surgeons. One must however keep in mind, that the indications for these techniques (a) should be carefully considered, (b) used only if morbidity is not increased and (c) when previously problematic or inacurate surgical methods can be improved upon. This study reports that, using a non-invasive fixation method (FISCOFIX-Cast), lesions between the ankle- and knee-joints can be precisely localized, registered and treated. Due to the difficult access to lesions especially in the posterior areas of the talus, using conventional arthroscopic methods this procedure is very useful. Percutaneous retrograde drilling (cf. [6, 7, 9, 15, 20, 21]) spared the joint's cartilage in all cases. At the level of the knee joint we see the usefulness of this method for complex situations (cf. [12, 13]) requiring precise drilling.

[Preoperative computerized tomography diagnosis of fractures of the tibial plateau]

Within the last decade computed tomography has become an important instrument for skeletal diagnosis. In this study the value of helical CT-scan was compared with plan X-rays and conventional tomography in 45 patients having sustained an intraarticular tibia plateau fracture. Between plan roentgenogramms and CT-scan the fracture classification according to the AO-classification was changed in 40% of all patients, in 39 cases the amount of impression or dislocation increased with a mean of 4.2 mm. Especially tiny fragments were better visible and therefore responsible for the shift of many B1 fractures to group B3. The difference between conventional tomography and computed tomography was less impressive, a change of fracture classification could be observed in only 6.7% of all cases.

Long-term results of arthroscopic partial lateral meniscectomy in knees without associated damage

We evaluated the outcome of partial lateral meniscectomy of 31 knees in 29 patients whose knees were otherwise normal. The mean follow-up was 10.3 years.

According to the Lysholm score, 14 knees were rated as excellent, four as good, five as fair and eight as poor, with a mean score of 80.5 points. Radiologically, only one lateral compartment was classified as grade 0, eight as grade 1, nine as grade 2, 11 as grade 3, and two as grade 4 according to Tapper and Hoover. No significant (p < 0.05) correlation was found between the amount of tissue resected and the subjective, clinical and radiological outcome.

Although early results of lateral meniscectomy may be satisfactory, we have demonstrated that in the long term there was a high incidence of degenerative changes, a high rate of reoperation (29%) and a relatively low functional outcome score.

Long-term results of arthroscopic partial lateral meniscectomy in knees without associated damage

We evaluated the outcome of partial lateral meniscectomy of 31 knees in 29 patients whose knees were otherwise normal. The mean follow-up was 10.3 years. According to the Lysholm score, 14 knees were rated as excellent, four as good, five as fair and eight as poor, with a mean score of 80.5 points. Radiologically, only one lateral compartment was classified as grade 0, eight as grade 1, nine as grade 2, 11 as grade 3, and two as grade 4 according to Tapper and Hoover. No significant (p < 0.05) correlation was found between the amount of tissue resected and the subjective, clinical and radiological outcome. Although early results of lateral meniscectomy may be satisfactory, we have demonstrated that in the long term there was a high incidence of degenerative changes, a high rate of reoperation (29%) and a relatively low functional outcome score.

Comparison of score evaluations and instrumented measurement after anterior cruciate ligament reconstruction

Forty-four patients who had undergone unilateral anterior cruciate ligament reconstructions were evaluated retrospectively with seven different scoring systems (International Knee Documentation Committee, Orthopadische Arbeitsgruppe Knie, Lysholm, Feagin and Blake, Zarins and Rowe, Cincinnati, and Marshall scores). The results varied between systems and therefore lacked reliability. Of the 44 patients, 32 were rated as excellent according to the Cincinnati score while only 3 patients were rated as normal according to the International Knee Documentation Committee form. Good and excellent results were found twice as frequently with the Cincinnati and Lysholm scores compared with the scores of Zarins and Rowe or the International Knee Documentation Committee form. Statistical analysis confirmed this observation and revealed significant differences between the scoring systems. Side-to-side differences using the manual maximum displacement test with the KT-1000 arthrometer revealed good correlation with the International Knee Documentation Committee and the Orthopadische Arbeitsgruppe Knie questionnaires. None of the other scoring systems, which do not measure anterior laxity, produced reasonable correlation with instrumented measurements. We found that certain population-specific factors as well as the distribution of single findings can distort the results of scoring systems. To avoid these interference factors, the patient sample should be homogeneous and selected prospectively and there should be agreement about the value of single findings.

[Comparison and outcome of grade II and III acromioclavicular joint injuries]

Eighty-five patients with grade 2 or grade 3 sprains of the acromioclavicular (AC) joint were evaluated clinically and radiographically 32 months after injury. Group I included 34 patients with grade 2 sprains (Tossy II) and group II included 51 patients with grade 3 injuries (Tossy III). In group I, 15 patients were treated surgically (group Ia) and 19 patients were treated conservatively (group Ib), while in group II, 41 patients were treated surgically (group IIa) and 10 patients were treated conservatively (group IIb). At surgery open reduction and transarticular fixation of the AC joint with Kirschner wires was performed. Conservative treatment included the initial use of a sling or a knapsack bandage and early performance of range-of-motion exercises. Shoulder function was assessed according to the score devised by Constant and Murley. In both groups, 97 of 100 possible points (minimum 72, maximum 100) were obtained after conservative and after surgical treatment. Nine of 10 patients (90%) with grade 3 sprains (group IIb) had more pronounced displacement and increased mobility of the lateral end of the clavicle after conservative treatment. After surgery, dislocation and increased horizontal, mobility of the lateral end of the clavicle occurred in 18 (44%) of 41 patients with grade 3 sprains (group IIa P < 0.0001). However, these findings did not correlate with the functional outcome. At follow-up there was a significant increase in degenerative changes seen on radiographs (P < 0.035) in all patients. Again these findings did not correlate with the functional outcome. More degenerative radiological changes were observed in patients who had undergone surgery (P < 0.003). Patients with grade 2 sprains were more frequently restricted in sporting activity after surgery (P < 0.05). Patients with grade 3 sprains who were treated surgically complained of pain more frequently (P < 0.01), and they returned to work later than patients who were treated conservatively after grade 3 sprains. An additional rehabilitation program guided by a physiotherapist seemed to have no impact on the functional outcome. A total of 56 patients were treated by surgery. Among these patients 11 complications occurred, requiring five additional surgical procedures. Among 29 conservatively treated patients, only in 1 patient did subacromially located arthritic changes of the AC joint have to be removed.