Objectives

Unicompartmental knee arthroplasty (UKA) is a demanding procedure, with tibial component subsidence or pain from high tibial strain being potential causes of revision. The optimal position in terms of load transfer has not been documented for lateral UKA. Our aim was to determine the effect of tibial component position on proximal tibial strain.

Objective: To compare the mechanical stability of fixation of bicondylar tibial plateau fractures using available internal and external fixation techniques.

Method: A bicondylar tibial plateau fracture was simulated on a uniform synthetic bone and tested with loading to failure. Following power calculations, seven tibias were used for each fixation method; five types of fixation were tested: 1) Dual plating. 2) Ring Fixator with inter-fragmentary screws. 3) Hybrid fixator (Ring-Bar) with interfragmentary screws. 4) Lateral plate and medial monolateral external fixator. 5) Lateral plate and medial interfragmentary screws. The specimens were tested in compression to failure. The vertical subsidence in either medial or lateral plateau was measured using an electrical transducer.

Results: In all cases the mode of failure was consistent with collapse occurring in the medial plateau. There was no significant difference in the ultimate strength between dual plating and the ring fixator [4218N, 4184N respectively; P=0.28, t test]. Failure was seen at lower loads with the other fixation systems (Table).

Conclusion: The Ring Fixator and dual plating demonstrated a greater strength and the most stable fixation, choice may depend on tissue viability and surgeon preference. Furthermore mobilisation of the patient may be undertaken earlier with more confidence using these two methods rather than less stable techniques.

Objective: To examine the relationship between three measurements of bone quality and bone strength of the tibial plateau, and the relationships between these measurements. Methods: The bone quality of sixteen cadaveric tibias was assessed for density and architecture using three methods: DXA, pQCT, and spectral analysis of digitised radiographs. These bone quality measurements were correlated with the þxation strength of a bicondylar plateau fracture, obtained by mechanical testing. Results: All three techniques correlate strongly with the mechanical strength of the þxed tibial plateau, with the highest correlation being with DXA (r=0.81, P< 0.001), and pQCT (r=0.79, P< 0.001); followed by spectral analysis (r= 0.5, P,0.01). DXA correlates strongly with pQCT (r=0.95, P< 0.001); Whereas, spectral analysis has a weaker correlation with both DXA (r=0.65, P< 0.01), and pQCT (r=0.69, P< 0.01). Discussion: This is the þrst study of bone quality assessment in the tibial plateau, and as with studies at other sites, DXA showed that BMD has the best correlation with mechanical failure. Both DXA and pQCT are a reßection of density assessment which explains the strong correlation seen. However, the strength of bone is a function of not just quantity and density but also its structure. This was assessed using spectral analysis which involves image processing and pattern recognition algorithm of the trabecular structure. This measures structure only and this may explain the lower correlation with bone strength. Nevertheless we feel that further analysis may demonstrate a speciþc use of this technique to compliment either DXA or PqCT in providing complete assessment of the bone.

Objective: To compare the mechanical stability of þxation of bicondylar tibial fractures using available internal and external þxation techniques. Method: A bicondylar tibial fracture was simulated on a uniform synthetic bone and tested with loading to failure. Following power calculations, seven tibias were used for each þxation method;þve types of þxation were tested: 1)Dual plating. 2)Ring Fixator with interfragmentary screws. 3)Hybrid þxator (Ring-Bar) with interfragmentary screws. 4)Lat-eral plate and medial monolateral external þxator. 5)Lateral plate and medial interfragmentary screws. The specimens were tested in compression to failure. The vertical subsidence in either medial or lateral plateau was measured using an electrical transducer. Results: In all cases the mode of failure was consistent with collapse occurring in the medial plateau. There was no signiþcant difference in the ultimate strength between dual plating and the ring þxator [4218N, 4184N respectively; P=0.28, t test]. Failure was seen at lower loads with the other þxation systems

Conclusion: The Ring Fixator and dual plating demonstrated a greater strength and the most stable þxation, choice may depend on tissue viability and surgeon preference. Furthermore mobilisation of the patient may be undertaken earlier with more conþdence using these two methods rather than less stable techniques.

Objective: To assess the inßuence of bone density on the þxation strength of bicondylar tibial plateau fractures. Method: Sixteen cadaver tibias were randomised into two groups to receive either dual plating or ring external þxation to stabilise a bicondylar tibial plateau fracture created with a standard method. The randomisation was stratiþed by BMD measured by DXA (above and below the mean). Cyclic axial compression tests were performed with increasing peak loads. Inter-fragmentary shear displacements were measured using four extensometers. Failure was deþned as over 3mm displacement. Results: There was a strong correlation between failure load and BMD [r=0.81, P< 0.001]. The mean failure load of the low BMD group (2701 N) was signiþcantly less than that with the high BMD (4530 N) [t-test=0.003]. The failure loads of the two þxation groups were not signiþcantly different (3520 N for the dual plating and 3710 N for the external þxation) [t-test=0.78]. BMD had a signiþcant effect on the failure load in the dual plating group [t-test=0.03], but not in the external þxation group [t-test=0.1]. Discussion: Failure of þxation has been reported as a common complication of bicondylar tibial plateau fractures with a rate as high as 30%. Osteoporosis and poor bone quality are considered important contributory factors. In our study this inßuence was evident with plating, but not with ring þxation. Ring þxation may be the preferred method of þxation for tibial plateau fractures in the elderly and osteoporotic patients.

A modified Kessel trans-acromial approach has been utilised in our Unit for decompression and repair of associated rotator cuff tear for all advanced impingement syndrome (Stage III). This preliminary report aims to review our results, and to assess the complications of this approach.

From 1996 to 1999, 22 consecutive patients who were treated surgically using a Trans-acromial approach for advanced impingement syndrome, were reviewed. The diagnosis of impingement syndrome was based on history, physical examination and Lignocaine impingement test, with either an ultrasound scan, arthrogram, or MRI. The modified trans-acromial approach was used involving splitting and raising a periosteal soft tissue flap over the acromion, followed by splitting the acromion in the coronal plane just behind the acromioclavicular joint, this allowed an extensive exposure of the rotator cuff and easy undercutting of the acromion.

20 patients were interviewed and examined specifically for this study, for an average follow up of 17 months. The other two patients were interviewed by telephone. The following parameters were studied: 1) functional assessment:[Constant’s Scoring system, and the UCLA Shoulder rating Scale. 2) Pain relief. 3) Patient satisfaction. 5) Return to preoperative activity. 6) Complication. The results were satisfactory in 17 patients (77%), and unsatisfactory in 5 pt (23%), one of which had cervical spondolysis, and two had new bony formation in the subacromial space. Pain relief was achieved in 78%. All patients returned to their preoperative occupation apart from one. Two patients had persisting impingement and had undergone revision subacromial decompression with satisfactory results.

The modified trans-acromial approach is an acceptable alternative to open anterior acromioplasty. It offers adequate decompression of the sub-acromial space, allowing a wide exposure and excellent visualisation of the rotator cuff. This facilitates cuff repair and mobilisation, while maintaining the integrity of the deltoid muscle, which accelerates postoperative rehabilitation.

To assess the outcome of Quadricepsplasty in limb reconstruction for stiff knees, and to analyze the contributing factors.

Thirteen patients underwent quadricepsplasty over the last 11-years for severe extension contractures of the knee, in the Limb Reconstruction Service. Ten cases were posttraumatic treated with External fixation, and three were non-traumatic causes, with an average interval between injury and quadricepsplasty of 10 years (range, 2–55). Eight patients had leg lengthening with an average of 6.5cm (range, 3–14), with simultaneous deformity correction. Post-operatively all the patients had continued passive motion except one with a fused hip.

Two to six weeks post-operatively, nine patients necessitated manipulation under anesthesia due to noteable loss of movement.

Preoperatively the average flexion was 24°(10–40), which improved in the operating room to 98°. After an average follow up of 15 months post-operatively they lost a mean of 18° flexion, with a final flexion 80°. Three patients developed an extension lag of 10° post-operatively. Two had deep infection with unsatisfactory results. Using Judet’s classification, we had 8 (53%) excellent or good, 6 (40%) fair, and one poor (7%) result.

The unsatisfactory results were associated with deep infection, long fixator time and a long interval between injury and quadricepsplasty.

Quadricepsplasty provides good results for severe extension contraction of the knee. Judet’s technique of disinsertion and muscle sliding addresses the problem of pin site tethering on the lateral side of the femur. Since this procedure is not free of complications and always demands intensive postoperative rehabilitation, it should be reserved for patients with severe extension contraction.