David Pokorný

Topographic variations of the relationship of the sciatic nerve and the piriformis muscle and its relevance to palsy after total hip arthroplasty

AbstractThe aim of this paper was to study the anatomical relationship between the piriformis muscle and the sciatic nerve with regard to the possibility of neurological deficit after THA. The incidence of anatomical variation of both structures is 15–30% in the literature. The authors studied 91 cadavers and found an atypical relationship in 19 cases (20.9%). In this study individual variations were found with the following frequency: The sciatic nerve exits below the piriformis muscle in 79.1% of the cases.The sciatic nerve separates into two divisions above the piriformis, one branch passing through the muscle, the other below it (14.3%).An unsplit nerve passes through the piriformis muscle in 2.2%.The nerve separates into two divisions above the piriformis, one branch exiting above the muscle and passing along its dorsal aspect, the second exiting distally below the muscle in 4.4%. The most common reasons for sciatic nerve injury in surgery of the hip joint are direct injuries, ischemia of the nerve tissue, compression or excessive distraction of the nerve, compression by bone cement, thermal damage during cement polymerization, injury during THA dislocation, compression by hematoma, bone prominence or an implanted acetabular component. According to the presented anatomical study, overstretching of the nerve itself or its branches in the area of the pelvitrochanteric muscles after their release from their origin can be another mechanism. Such overstretching can appear in the presence of some of the aforementioned anatomical variants.

Isolated talonavicular arthrodesis in patients with rheumatoid arthritis of the foot and tibialis posterior tendon dysfunction

BackgroundThe foot is often affected in patients with rheumatoid arthritis. Subtalar joints are involved more frequently than ankle joints. Deformities of subtalar joints often lead to painful flatfoot and valgus deformity of the heel. Major contributors to the early development of foot deformities include talonavicular joint destruction and tibialis posterior tendon dysfunction, mainly due to its rupture.MethodsBetween 2002 and 2005 we performed isolated talonavicular arthrodesis in 26 patients; twenty women and six men. Tibialis posterior tendon dysfunction was diagnosed preoperatively by physical examination and by MRI. Talonavicular fusion was achieved via screws in eight patients, memory staples in twelve patients and a combination of screws and memory staples in six cases. The average duration of immobilization after the surgery was four weeks, followed by rehabilitation. Full weight bearing was allowed two to three months after surgery.ResultsThe mean age of the group at the time of the surgery was 43.6 years. MRI examination revealed a torn tendon in nine cases with no significant destruction of the talonavicular joint seen on X-rays. Mean of postoperative followup was 4.5 years (3 to 7 years). The mean of AOFAS Hindfoot score improved from 48.2 preoperatively to 88.6 points at the last postoperative followup. Eighteen patients had excellent results (none, mild occasional pain), six patients had moderate pain of the foot and two patients had severe pain in evaluation with the score. Complications included superficial wound infections in two patients and a nonunion developed in one case.ConclusionsEarly isolated talonavicular arthrodesis provides excellent pain relief and prevents further progression of the foot deformities in patients with rheumatoid arthritis and tibialis posterior tendon dysfunction.

Wrist arthrodesis in rheumatoid arthritis. A new technique using internal fixation.

Arthrodesis of the wrist is a standard operation which is indicated for severe rheumatoid arthritis in which destruction is too advanced for more conservative procedures, or after failure of previous surgery. We have developed an L-shaped plate designed for this purpose. It provides rigid internal fixation with the wrist in the neutral position and utilises bone grafts obtained from the distal ulna and the carpal bones. We have carried out 29 successful fusions between 1992 and 1995. In all 29 patients synovectomy and resection of the head of the ulna were performed; 11 also had reconstruction of ruptured extensor tendons. All the patients obtained bony union, pain relief and improved function.

Treatment of orthopedic infections caused by resistant staphylococci.

During 1999–2005 we treated 15 patients with linezolid for relevant infections of locomotion apparatus (7 cases with endoprosthesis infection, 5× osteomyelitis and 3× another infection). With the exception of one case the antibiotic therapy was always combined with appropriate surgical intervention. Average period of linezolid administration was 26 d; linezolid was applied from the beginning intravenously on average for 10 d, and then orally for 16 d (average). There were no undesirable effects in the file. Success rate reached 86.6 %. MRSA strains were proved by standard methods: growth on Mueller-Hinton agar with increased concentration of NaCl and 2 mg/L of oxacilline, and measuring inhibitory zones around cephoxitine disk. The sensitivity to other antibiotics was specified by disk-diffusion test; that to linezolid was verified by E-test. Linezolid represents a medical reserve for the treatment of multiresistant Gram-positive infections or for emergencies, when allergy onset, high toxicity risk, intolerance,etc. do not allow to use other,in vitro effective, antibiotics.

Ankle block implemented through two skin punctures.

Background: Recently, peripheral nerve blocks have increasingly been used in orthopedic surgery. The foot block is an alternative for anesthesia in cases of forefoot and midfoot operations. We propose a modification of the block technique due to potential difficulties concerning the tibial nerve. Materials and Methods: The spatial position of the tibial nerve in the neurovascular bundle, proximal to entering the tarsal tunnel and sural nerve behind lateral malleolus was measured on 60 dissected preparations. Modification of the block technique was proposed. A tibial nerve block was administered by inserting a needle, at an area above the upper edge of the heel bone, tangential to the Achilles tendon. The needle was then withdrawn and redirected to the frontal plane and inserted through the tissue, anterior to the Achilles tendon and laterally behind the lateral malleolus to block the sural nerve. A block of the saphenous nerve superficial and deep peroneal nerves was implemented by needle insertion subcutaneously two centimeters proximal to the crest of the ankle joint. The technique was then evaluated in the clinical part of the study in 84 operative procedures. Results: The tibial nerve is located 21.1 mm ± 2.1 mm from the medial aspect of the Achilles tendon and 11.6 mm ± 1.3 mm deep in the neurovascular bundle. The distance from the posterior margin of the lateral malleolus to the sural nerve is 18.3 mm ± 1.9 mm. We achieved a 93% success rate in implementation of the complete foot block in 84 operations. Conclusion: The technique, proposed in the anatomical portion of the study and evaluated in the clinical part, had a similar success rate when compared to techniques published in the literature. Though comparable to currently used techniques, this technique provides easier positioning of a patient and a complete block of the foot can be done with two skin injection sites. Level of Evidence: IV, Case Series

Attachments of muscles as landmarks for implantation of shoulder hemiarthoplasty in fractures

BACKGROUND The attachments of muscles and the position of the humeral head are important for a good functional outcome of shoulder hemiarthroplasties after displaced fractures of the proximal humerus. Deviations in the attachments and changes in their spatial position with respect to the humeral head during surgical reconstruction change the biomechanics and reduce the range of motion of the should joint postoperatively. METHODS AND RESULTS We used 198 humerus preparations and using 3-dimensional analysis measured the angular relationships between the humeral head axis and medial margin of the greater tuberosity (11.9 degrees +/- 9.1 degrees ), lateral margin of the lesser tuberosity (48.0 degrees +/- 7.8 degrees ), and the crest of the greater tuberosity (27.1 degrees +/- 9.6 degrees ). CONCLUSION This study provides average values of the positions of the greater and lesser tuberosities with respect to the humeral head axis. We show that the greater and lesser tuberosities are more reliable than the transepicondylar line for reconstruction of humeral head retroversion. LEVEL OF EVIDENCE Basic Science.

Patient-specific hip geometry has greater effect on THA wear than femoral head size.

In vivo linear penetration in total hip arthroplasty (THA) exhibits similar values for 28mm and 32mm femoral head diameter with considerable variations between and within the studies. It indicates factors other than femoral head diameter influence polyethylene wear. This study is intended to test the effect of patient׳s individual geometry of musculoskeletal system, acetabular cup orientation, and radius of femoral head on wear. Variation in patient׳s musculoskeletal geometry and acetabular cup placement is evaluated in two groups of patients implanted with 28mm and 32mm THA heads. Linear wear rate estimated by mathematical model is 0.165-0.185mm/year and 0.157-0.205mm/year for 28 and 32mm THA heads, respectively. Simulations show little influence femoral head size has on the estimated annual wear rate. Predicted annual linear wear depends mostly on the abduction angle of the acetabular cup and individual geometry of the musculoskeletal system of the hip, with the latter having the greatest affect on variation in linear wear rate.