Wai Lam Chan

Comparison of total knee arthroplasty using computer-assisted navigation versus conventional guiding systems: a prospective study

Purpose. To compare knee alignments in total knee arthroplasty (TKA) using computer-assisted navigation versus conventional guiding systems. Methods. Five men and 49 women aged 49 to 79 years underwent TKA for primary osteoarthritis of the knee with varus deformity. All valgus knees were associated with inflammatory arthritis and thus excluded. Computer-assisted navigation was used for the first 35 TKAs, whereas conventional extramedullary tibial and intramedullary femoral guiding systems were used for the next 35 TKAs. The mechanical axis, coronal tibial and femoral angles, sagittal tibial and femoral angles in the 2 groups were compared. Results. Sagittal tibial and femoral angles aligned more optimally in TKAs using computer-assisted navigation. In the respective computer-assisted navigation and conventional guiding systems, 33 (94%) and 26 (74%) of the TKAs attained a postoperative mechanical axis of <3° varus/valgus. Conclusion. Computer-assisted navigation gives a more consistent alignment correction and reduces outliers during implant positioning.

Anatomic variations of neurovascular structures of the ankle in relation to arthroscopic portals: a cadaveric study of Chinese subjects.

Purpose. To investigate anatomic variations of neurovascular structures in the ankle and the safety margin for arthroscopic portals. Methods. 11 left and 12 right ankles from 8 female and 15 male fresh cadavers of Chinese ethnicity aged 53 to 88 (mean, 68) years were used. The ankle was standardised in a plantigrade position, zero-degree inversion, and neutral rotation. Four ankle portals, namely anteromedial (AM), anterolateral (AL), posteromedial (PM) and posterolateral (PL), were identified using 23-gauge needles. Skin and subcutaneous fat were dissected from the underlying fascia to visualise neurovascular structures. Distances were measured from: (1) the AM portal to the saphenous vein and nerve and its branches, (2) the AL portal to branches of the superficial peroneal nerves, of which the lateral one was labelled as the intermediate dorsal cutaneous branch and the medial one as the medial dorsal cutaneous branch, (3) the PM portal to the posterior tibial neurovascular bundles, and (4) the PL portal to the sural nerve. Results. The distances from (1) the AM portal to branches of the great saphenous vein and nerve, and (2) the AL portal to the intermediate dorsal cutaneous branch of the superficial peroneal nerve were short and may be an anatomic hazard. Variations were significant among the cadavers in terms of distances of the portals to the neurovascular structures. Conclusion. In Chinese cadavers, variations of neurovascular structures are significant. Care must be taken to avoid inadvertent injury during ankle arthroscopy.

Hyaluronic acid instillation following arthroscopic anterior cruciate ligament reconstruction: a double-blinded, randomised controlled study

Purpose. To assess the effect of hyaluronic acid instillation after arthroscopic anterior cruciate ligament (ACL) reconstruction for improving pain, range of movement, and function of the knee. Methods. 28 men and 4 women underwent arthroscopic ACL reconstruction for isolated ACL rupture (partial or complete) and instability after recreational sports injury 2 to 120 months earlier. They were randomised to undergo arthroscopic ACL reconstruction followed by intra-articular viscoseal instillation (13 men and 3 women) or arthroscopic ACL reconstruction alone (15 men and 1 woman). The knee injury osteoarthritis outcome score (for pain, symptoms, activities of daily living, sport and recreation function, and quality of life), range of movement, knee circumference, and analgesic use were assessed on days −1, 1, and 2, and weeks 2, 6 and 12. Results. Patient demographics were similar at baseline. At postoperative days 1 and 2, all subscales of the knee injury osteoarthritis outcome score (except for quality of life) were significantly higher in the viscoseal group. At weeks 2, 6, and 12, improvement in both groups equalised. Knee swelling (change in knee circumference) was significantly less in the viscoseal group at days 1 and 2 (p=0.009 and p=0.038, respectively, Mann-Whitney U test). Only one patient in the viscoseal group had a limited range of movement. No patient developed any adverse reaction. Conclusion. Intra-articular viscoseal instillation improved pain control and swelling 2 days after arthroscopic ACL reconstruction.

Breakage of intramedullary femoral guide rod during total knee arthroplasty: a case report

We report a rare complication during primary total knee arthroplasty. An intramedullary femoral guide rod was broken during insertion. The broken part jammed into the isthmus of the femur. An initial attempt to push the broken rod via the proximal femur by a guide wire to the distal femur was unsuccessful because the broken rod was lodged in the isthmus. Ultimately, the isthmus was opened using a flexible 9-mm end-cutting reamer, and the broken rod was pushed down to the distal femoral entry site in an antegrade fashion under image intensification. Selecting a more medial entry site on the intercondylar notch with a smaller valgus cutting angle and using a shorter guide rod can avoid such a breakage.

Rotary subluxation of the metacarpophalangeal thumb joint: a case report

Irreducible rotary subluxation of the metacarpophalangeal joint (MCPJ) of the thumb is a rare entity. Open reduction is indicated when signs of irreducibility are seen on the radiographs. We present one such case caused by displacement of the sesamoid bone into the intercondylar notch of the first metacarpal bone. A 35-year-old woman sustained a twisting injury to her right thumb by pronating and hyperextending it while attempting to retrieve things that she had dropped into a basin conduit. True lateral radiographs showed rotary subluxation of the thumb MCPJ, a sesamoid bone overlapping with the metacarpal head, and loss of the subsesamoid joint space and an incongruent MCPJ on full flexion. A high level of clinical suspicion is needed to diagnose this rare entity.

Atypical periprosthetic femoral fracture: a case report

We report an 82-year-old woman who underwent fixation with a long-spanning cable-plate for a bisphosphonate-induced Vancouver B1 periprosthetic femoral fracture. Non-union and breakage of the plate occurred at 16 months and necessitated revision surgery using a long-stem femoral prosthesis augmented with a cable-plate construct. Bone union was achieved eventually after 10 months.

Magnetic Resonance Imaging of the Subcoracoid Region and Its Relationship with Subscapularis Lesions in the Chinese Population: 在中國人群組中用磁力共振來評估下喙突區域及其與肩胛下肌病變的關係

Introduction: Coracoid impingement is considered a known yet frequently overlooked cause of anterior shoulder pain. Subcoracoid stenosis has been shown to be related to subscapularis tear. Studies have shown that patients with coracoid impingement have a shorter coracohumeral distance (CHD) and a larger coracoid overlap (CO) but these are based on data from Western populations. The aim of our study was to provide a local database on the MRI measurement of these parameters in our Chinese population and raise the awareness of this disease entity. Methods: All the shoulder MRI films taken in our hospital in 2011 were retrospectively reviewed and classified into two cohorts. The control group consisted of patients who had no subscapularis lesion. The subscapularis lesion group consisted of patients with complete tear, partial tear or abnormal signal over the subscapularis tendon. The CHD and CO were measured. Results: We reviewed 133 sets of shoulder MRI obtained in our hospital during 2011. Thirteen patients were noted to have subscapularis lesion. The CHD in the subscapularis lesion group was 6.24 ± 2.18 mm. The CHD in the control group was 9.95 ± 3.9 mm. Women had shorter CHD (8.18 ± 2.57 mm) than men (11.0 ± 4.54 mm). We failed to notice any statistically significant difference with regards to CO, coracoid process and lesser tuberosity morphology between the two groups of patients. Conclusion: MRI assessment of CHD can be useful in identifying patients at risk of having subscapularis lesion and coracoids impingement.

Tibial tuberosity–trochlear groove distance in Chinese patients with or without recurrent patellar dislocation

Purpose. To compare the tibial tuberosity–trochlear groove (TTTG) distance in Chinese patients with or without recurrent patellar dislocation. Methods. The TTTG distance of 14 knees in 5 men and 9 women aged 16 to 38 years with recurrent patellar dislocation were compared with that of 73 control knees using magnetic resonance imaging. Results. The mean TTTG distance was significantly greater in patients with recurrent patellar dislocation than in controls (16.4 mm vs. 10.1 mm, p<0.001). Six (43%) knees with recurrent patellar dislocation had the TTTG distance greater than the cut-off threshold of 16.4 mm, compared to none in controls. Conclusion. The TTTG distance is related to height and is shorter in Chinese than Caucasian patients; the threshold for tibial tuberosity transfer should be lower in Chinese patients.

Are the Current Size Options of Glenoid Baseplates for Reverse Shoulder Arthroplasty Sufficient for our Local Population?: 現有反置式人工肩關節置換術中盂底板組件的大小選項是否滿足我們本地人口的需要？

Background/Purpose Reverse shoulder arthroplasty (RSA) is an effective treatment for patients who suffer from shoulder pain and dysfunction associated with a variety of shoulder pathologies including severe rotator cuff deficiency with or without glenohumeral arthritis. It has been widely used in European countries and the United States and is now gaining popularity in Asia, including Hong Kong. However, there are only limited size options available for glenoid baseplates, with 25 mm being the smallest size in some commonly used systems. The aim of our study is to perform computerized tomography (CT) measurements of the glenoid dimension in the Chinese population and to see if the current glenoid baseplate component size option is sufficient for our local population. Methods A total of 70 CT scans of shoulder regions were analysed. Measurements included maximum superoinferior height and the anteroposterior height. Results The glenoid dimensions were smaller compared to those from previous studies in Caucasian counterparts. Some 41% of female glenoids had widths measuring < 25 mm (25 mm being the smallest size available in some commonly used RSA systems). Conclusion Although there are only limited size options available for the glenoid baseplate in RSA, from our data, it should be able to cover most patients in our local population. However, surgeons should exercise special care when contemplating performing reverse shoulder replacement for small size females in our local population.

Magnetic Resonance Imaging Assessment of the Femoral Tunnel Position in Medial Patellofemoral Ligament Reconstruction: 用磁共振掃瞄來評估在內側髕韌帶重建手術中股骨隧道的位置

Background/Purpose Correct femoral tunnel position in medial patellofemoral ligament (MPFL) reconstruction is essential to maintain proper biomechanics of the patellofemoral joint throughout the range of movement. Several techniques have been described for MPFL reconstruction, however, there are few reports describing the accuracy of femoral tunnel positioning assessed postoperatively. Methods Ten patients having recurrent patellar dislocation with MPFL reconstruction performed in our centre from 2009 to 2013 were analysed. Femoral tunnel position was guided by intraoperative X-ray with landmarks described by Schottle et al, 2007. Postoperative magnetic resonance imaging (MRI) was performed on both knees, and femoral tunnel was assessed with reference to the femoral origin of the MPFL in the nonoperated side. Results All cases showed an intact MPFL graft, with the majority demonstrating satisfactory femoral tunnel position based on postoperative MRI. Conclusion MPFL reconstruction with anatomic positioning of the femoral tunnel guided by intraoperative X-ray showed satisfactory accuracy in postoperative MRI results, indicating that a well-positioned MPFL graft results in better clinical outcomes.