Lars Ingvar Hansson

Three-dimensional instability of the anterior cruciate deficient knee

Using roentgen stereophotogrammetry we have recorded the three-dimensional movements of the knee during an anteroposterior laxity test in 36 patients with torn anterior cruciate ligaments and in three cadaver knees. At 30 degrees of knee flexion and before loads were applied the tibia occupied a more laterally rotated position if the anterior cruciate ligament had been injured. When the tibia was pulled anteriorly knees with cruciate deficiency rotated more laterally and were more abducted than normal knees. Posterior traction induced lateral rotation in the injured knee and medial rotation in the intact one. Precise knowledge of the three-dimensional instability of the anterior cruciate deficient knee may be important when the laxity is evaluated only in relation to one of the three cardinal axes.

Fracture of the lower extremity after total hip replacement

SummaryThe incidence of ipsilateral fracture of the lower extremity after total hip replacement (THR) was evaluated in 1442 THRs performed between 1968 and 1983. Twenty-two fractures had occurred, of which 14 were femoral. Twelve of the femoral fractures occurred in women and two in men. The accumulated postoperative risk of femoral fracture during an observation period of 15 years was 25.3 per 1000. Short femoral stems were associated with proximal femoral fractures and long stems with more distal femoral fractures. No specific preoperative diagnosis such as arthrosis, rheumatoid arthritis, or femoral neck fracture was associated with significantly increased incidence of postoperative fractures.

Instability of total hip prostheses at rotational stress. A roentgen stereophotogrammetric study.

Roentgen stereophotogrammetric analysis (RSA) has been carried out on 24 total hip prostheses (24 patients), which were all painful at weightbearing. The examinations were made with the hip at distraction, compression, external and internal rotation. One acetabular component showed instability only at distraction-compression and one showed instability only at rotation. Four femoral components showed instability at distraction-compression and at rotation, six only at rotation, but none showed instability only at distraction-compression. Thus rotational provocation demonstrated instability in all unstable femoral components; rotational stress must be of importance in mechanical loosening of the femoral component.

Definition of endoprosthetic loosening: Comparison of arthrography, scintigraphy and roentgen stereophotogrammetry in prosthetic hips

Contrast arthrography, radionuclide arthrography, scintigraphy and roentgen stereophotogrammetric analysis (RSA) were used to detect mechanical loosening in 14 painful total hip replacements. All prosthetic components unstable by RSA, or with abnormal arthrogram, or with increased scintigraphic activity, or loose at revision were migrating, but no non-migrating components demonstrated any of these signs of loosening. Our findings indicate that mechanical loosening should be defined as migration.

Two-year follow-up of femoral neck fractures: Comparison of osteosynthesis methods

For 14 consecutive months, all 152 femoral neck fracture patients greater than or equal to 50 years of age admitted to the Lund University Hospital were operated on with two hook-pins if born on an uneven date and a four-flanged nail if born on an even date. A clinical 2-year follow-up revealed a 35 per cent mortality. Among survivors, radiographic healing complications were seen in undisplaced fractures in 1/13 pinned and 5/14 nailed (p greater than 0.05) and in displaced fractures in 12/36 pinned and 23/32 nailed (p less than 0.01). This outcome correlated well with the early postoperative scintimetry. Reoperation within 2 years had been performed for seven pinned and 19 nailed fractures. In hook-pinning, thus, less than one patient out of 12 needed a reoperation with THR within 2 years. This figure is interpreted as strongly favouring hook-pinning before arthroplasty as the primary procedure in femoral neck fracture.

Mobility of the lateral malleolus: A roentgen stereophotogrammetric analysis

In nine children and adolescents, the motion of the distal fibula in relation to the tibia was measured by roentgen stereophotogrammetry. Between the extremes of ankle flexion, the fibular epiphysis moved on average 1.4 mm.

Chronic anterolateral instability of the knee A roentgen stereophotogrammetric evaluation

The rotatory stability of the knee was investigated in 20 patients with a previous tear of the ACL. The three- dimensional movements of the tibia during the testing procedure were registered using roentgen stereopho togrammetric analysis. Changes of the tibial move ments between an intermediate, an anterior, or a pos terior tibial position were registered using tibial tractions in combination with a simultaneous external or internal rotatory torque. At 20° of flexion the internal rotatory laxity was increased on the injured side. The external rotatory laxity did not significantly differ between the two sides. With anterior traction, the internal rotatory laxity in creased on both the injured and the normal sides and became almost equal. The external rotatory laxity man ifested a decrease which was most pronounced on the injured side. With posterior traction, the rotatory laxities decreased and did not significantly differ between the two sides. Analysis of the simultaneously occurring translations of the tibial plateau disclosed abnormal displacements of both the medial and the lateral tibial condyles on the injured side.

Poor fixation of the Mittelmeier hip prosthesis A clinical, radiographic, and scintimetric evaluation

We have evaluated 30 Mittelmeier hips on an average 3.3 years after the operation. Seven hips had been revised because of severe pain and mechanical loosening and one because of fracture of the threaded ceramic cup. Only five of the remaining 22 hips were asymptomatic. There was radiographic migration of the acetabular and femoral components in more than one third of the hips and increased scintimetric values around the femoral component in all but two hips. Unfavorable design of the Mittelmeier prosthesis may be an important etiologic factor contributing to poor component fixation and inferior clinical results.

Modification of Bone Formation Rate by Growth Hormone, Melanocyte-Stimulating Hormone, and Cortisone in the Normal Rat

Bone growth and remodelling was studied in rats after injection of growth hormone, melanocyte-stimulating hormone (alpha-MSH), and cortisone daily for 20 days with tetracycline as intravital marker. An increase of both longitudinal and periosteal growth with growth hormone was found. A decrease of both was found after a high cortisone dose. Lower cortisone doses seem to have stimulated periosteal growth. No effect of alpha-MSH was found.

Stability of femoral neck fractures: A postoperative roentgen stereophotogrammetric analysis

Using roentgen stereophotogrammetric analysis, the postoperative stability of femoral neck fractures was measured in 16 patients. During the first day after internal fixation, before weight bearing, the center of the femoral head moved on an average 1.5 mm (total translation) in six undisplaced fractures and 3.7 mm in 10 displaced fractures, which was about one third of the fracture movement during the first postoperative month. Three undisplaced fractures displayed a rotatory instability, mainly after weight bearing had begun. Five of the displaced fractures showed maximal rotatory displacement during the first postoperative day. The recorded fracture movements before weight bearing may question the rationale of peroperative mechanical compression.