Ronald L. Linscheid

Muscles across the elbow joint: A biomechanical analysis

Abstract In order to understand the mechanics of the human musculoskeletal system, quantitative data on the functional anatomy of the muscles related to the joint are necessary. Several important biomechanical parameters of the muscles controlling the elbow joint were determined. Serial cross-sectional anatomy analysis was used to obtain the centroid and thus the moment arms of each of the muscles along the upper arm and at the elbow joint. Muscle volume and true fiber length at the resting position were also measured. From these data, the physiological cross-sectional areas were calculated. The volume provided the information on the work capacity of the muscles. The physiological cross-sectional area provided the potential tension which the muscle can generate.

Difficult wrist fractures. Perilunate fracture-dislocations of the wrist.

Perilunate dislocations of the wrist have a common pathway of disruption that occurs from extensive dorsiflexion injuries. Open reduction and internal fixation of these injuries is required to provide accurate alignment and the option for ligament repair. Both dorsal and palmar surgical incisions may be indicated. Associated injuries to the median nerve must be recognized. Treatment includes scaphoid and radial styloid stabilization with multiple K-wires or internal compression screw (Herbert or Association for the Study of Internal Fixation [ASIF] screws). In these injuries, the lunate must be reduced first and stabilized. The scaphoid proximal segment follows the lunate unless the scapholunate (SL) ligament is torn. The distal scaphoid fragment, capitate, and triquetrum are reduced and aligned with the lunate and need to be held with K-wires. Ligament repair and augmentation may be necessary at both scapholunate and lunotriquetal areas if there has been serious ligament injury. Palmar ligament repair is often required, and we recommend a palmar exploration in most patients along with release of the median nerve. Surgical treatment results of perilunate fracture-dislocations of the wrist appear better than conservative treatment methods, but complications following both indicate the need for improved internal fixation and fracture-dislocation realignment. These fractures are a real challenge to the treating surgeon who must use patience, precise surgical techniques, and careful roentgenographic study (including tomograms and traction views) to assure the best result.

External pin fixation for unstable Colles' fractures.

During a five-year period, a double-pin Roger Anderson apparatus, with pins perpendicularly placed in the second and third metacarpals and in the distal part of the radius, was applied in 130 patients with an unstable Colles fracture. Sixty of the 130 were followed for two years. Shortening was limited to a median of two millimeters and dorsal angulation, to a median of 3 degrees. Wrist dorsiflexion averaged 58 degrees, and volar flexion averaged 50 degrees. Pronation and supination had an average loss of 5 degrees when compared with the uninjured side. Repeat reduction was required in only three patients. Patient assessment revealed that 85 per cent of the patients had good results; 12 per cent, fair; and 3 per cent, unsatisfactory. Objective analysis (McBride system) revealed that 90 per cent had good to excellent results; 8 per cent, fair; and 2 per cent, poor. Ninety-two per cent had no pain, 89 per cent had no deformity, and the mean grip strength was twenty kilograms. Sixteen patients had complications; seven of the sixteen had pin loosening, which occurred most frequently late during the course of treatment and without adverse sequelae.

Perilunate dislocations and fracture-dislocations : a multicenter study

A series of 166 perilunate dislocations and fracture-dislocations from 7 centers was retrospectively studied. The diagnosis was missed initially in 41 cases (25%). A classification system was presented. The perilunate fracture-dislocations were more frequent than the perilunate dislocations at a ratio of two to one. The displacement was dorsal in 161 cases (97%) and palmar in only 5 (3%). The dorsal transscaphoid perilunate fracture-dislocations represented 96% of the dorsal perilunate fracture-dislocations and 61% of the whole series. The clinical and radiologic outcome of 115 perilunate dislocations and fracture-dislocations with at least 1 year and an average of 6 years 3 months of follow-up was studied. Open injury and delay of treatment had an adverse effect on clinical results, whereas anatomical type had less influence. In cases treated early, the clinical results were satisfactory but the incidence of post-traumatic arthritis was high (56%). In the dorsal perilunate dislocation group of pure ligamentous injuries and in the dorsal transscaphoid group, the best radiologic results were observed after open reduction and internal fixation. In the latter group, the fixation of the scaphoid alone was not always sufficient and left occasionally scapholunate dissociation, lunotriquetral dissociation, ulnar translation of the carpus, or other carpal collapse patterns. The initial appraisal of both the osseous and ligamentous pathology was very important.

Fractures of the scaphoid: a rational approach to management.

Fractures of the scaphoid can be classified into either undisplaced, stable fractures or displaced, unstable fractures by their roentgenographic appearance. When there is greater than 1 mm of fracture offset or an instability collapse pattern (dorsal lunate rotation) on the lateral view, an unstable, displaced fracture is present. When doubt exists after reviewing routine films, special X-rays, such as radial-ulnar deviation stress views, traction oblique views, or trispiral tomography should be obtained. In acute scaphoid fractures, where no displacement of the fracture fragments or lunate dorsal tilting can be seen, a short-arm thumb spica cast provides satisfactory support for fracture union. A wrist position of volar flexion-radial deviation is preferred to the more traditional positions of wrist extension with radial deviation or wrist extension with ulnar deviation with 100% union rate and no malunions. In displaced scaphoid fractures, a long-arm cast is recommended, with reduction of the fracture by wrist flexion and radial deviation. If accurate reduction is not obtained or is lost during the course of treatment, open reduction and internal fixation should be strongly considered. In scaphoid nonunions, undisplaced fractures can be treated satisfactorily by an inlay bone graft, using either a dorsal or a volar approach. For displaced scaphoid nonunions, either a dorsal approach with internal fixation should be done (particularly if there is evidence of radioscaphoid arthrosis), or a volar approach with internal fixation can be performed. Peg graft techniques had a higher rate of nonunion and secondary arthritis. Nonunions should be immobilized a minimum of 4 months or until roentgenographic union is present.

Total elbow arthroplasty. A five-year experience at the Mayo Clinic.

During the five years from 1973 through 1977, eighty Mayo and Coonrad total elbow arthroplasties were performed in seventy-two patients at the Mayo Clinic. Follow-up after at least two years (average, four years) revealed that the results were good in 60 per cent, fair in 16 per cent, and poor in 24 per cent. Pain was a major symptom in 80 per cent of the elbows preoperatively but in only 3 per cent postoperatively. At follow-up, motion had increased: extension-flexion by 10 degrees (average range, 29 to 131 degrees of flexion) and forearm rotation by 26 degrees (average range, 61 degrees of pronation to 59 degrees of supination). Excluding eleven prostheses with loosening for which revision was necessary, there were forty-four complications (55 per cent) after eighty procedures. Of these forty-four complications, eleven were ulnar neuropathies (two permanent and nine transient); four were wound-healing problems; ten, significant triceps weakness; eleven, intraoperative fractures of the medial or lateral supracondylar bone column; seven, deep infections; and one was an ulnar fracture. Although the complication rate was very high, most of the complications occurred during the early years of the study. Follow-up revealed twenty-nine elbows with radiolucency around the components: in twenty-five about the humeral and in four about the ulnar component. Revisions were performed in nineteen (24 per cent) of the eighty elbows: in eleven because of loosening, in seven because of deep infection, and in one because of ankylosis. Intraoperative supracondylar fracture and defective cementing of the prosthesis were important factors contributing to prosthetic loosening. When the arthroplasty was successful, the relief of pain was dramatic, stability was excellent, and the range of motion was superior to that provided by any other procedure currently available.

Normative model of human hand for biomechanical analysis

Abstract A three-dimensional normative model of the hand was established, based on the averaged anatomical structure of ten normal hand specimens. The joint and tendon orientations were defined from biplanar X-ray films. The configurations of the hand at the joints were described by the classic Eulerian angles. Force potential and moment potential parameters were utilized to describe the contribution of each tendon in the force analysis. The mean values of these two parameters were used to compute the designated two points for each tendon at each joint in the normative model. With appropriate coordinate transformations at the joints, the tendon locations and excursions under various functional configurations can be computed. This model can be used to perform force and motion analyses for both normal and pathological hands.

The distal radioulnar ligaments: A biomechanical study

The mechanical roles of the triangular fibrocartilage have been examined in three experiments. Kinematic analysis by a stereophotogrammetric method revealed that the palmar radioulnar ligament was taut in supination and that the dorsal radioulnar ligament was taut in pronation. In full pronation, the palmar radioulnar ligament decreased to an average of 71% of its length in tension. In full supination, the dorsal radioulnar ligament decreased to an average of 90% of its length. Mechanical testing of the triangular fibrocartilage under axial load disclosed a significant laxity (mean: 10.4 mm), which was decreased in pronation. Transverse loading tests demonstrated that the triangular fibrocartilage is less stiff in neutral forearm rotation. Study of the material properties of the palmar and dorsal parts of the triangular fibrocartilage showed these structures to be strong ligaments with material properties similar to those of the radiocarpal ligaments.

Nonunion of the scaphoid: Analysis of the results from bone grafting

Scaphoid nonunion was treated by bone-grafting techniques in 86 patients with 90 scaphoid fractures. The volar inlay (Russe) technique had union in 38 of 44 fractures (86%); the dorsal inlay (Matti) technique in 20 of 22 fractures (91%); the dorsal peg graft (Murray) in nine of 18 fractures (50%); and compression screw osteosynthesis in one of six cases (17%). Fourteen patients had secondary arthritis associated with fracture union. Union was more frequent (85%) in 54 undisplaced nonunions than in 36 displaced nonunions (65%). Complications included avascular necrosis, secondary arthrosis, and persistent nonunion. Avascular necrosis in 13 nonunions was treated successfully by inlay grafts in 11, and postoperative avascular necrosis (four nonunions) was resolved after fracture healing in two. The four patients with failed results had the dorsal peg grafting technique. Of 22 persistent nonunions, 16 had secondary arthritis and four had avascular necrosis. The rate of union was increased when Kirschner wire fixation of unstable nonunions was performed. The dorsal and volar inlay techniques had consistently higher rates of union with fewer complications than did the dorsal peg grafting technique.

Relative motion of selected carpal bones: A kinematic analysis of the normal wrist

The relative motion of selected carpal bones and the radius was studied using five cadaver specimens labeled with metal markers to precisely quantitate their motions. Data was obtained by means of a combination of orthoradiography, sonic digitization, and computer analysis. We conclude that the wrist functions as two carpal rows with the distal row bones relatively tightly bound to one another and the proximal row bones less so but still moving together. Therefore, we theorize that the proximal row functions as a variable geometry intercalated segment between the distal row and the radius-triangular fibrocartilage.